Injection Limiter adjustment

[t***@gmail.com]

I've got a Yanmar 2gm20 that I'm pretty convinced has a problem with
the governor (speed is not well controlled especially when it comes
under load). The seemingly easy path is to fiddle with the injection
limiter. However, there are a couple of things holding me back.
First, they put a wire seal on the adjuster back at the factory. I've
had the problem from day one so I suspect that they didn't get the
adjustment right, but still I figure they sealed it for a reason. I'm
no Japanese scholar but it may even say "Tom, keep your **** hands off
this!" So, will really bad things happen if I mess with the limiter?
Second, I'm not sure exactly how to go about making the adjustment
should I care to. The manual says "if the engine does not accelerate
smoothly turn the limiter slightly counter-clockwise." Good, that's
my problem. The drawing shows a cap nut, lock nut and injection
control shaft. I presume I have to remove the nuts and back the
injection control shaft off a fraction. But, the drawing doesn't show
a slot or anything on the control shaft to keep it from turning while
I move the nuts. Is there some trick to making this work I should know
about when I attempt this? It'd be really nice if I could mark things
so I could at least get back to the current settings if fiddling
doesn't fix things. But how? Thanks!

-- Tom.

[Roger Long]

You should take a look at www.boatdiesel.com its has both general and
manufacturer specific forums. You may find your answer just by browsing
around. You can find out a lot for free but I think the $25.00 I paid for a
year membership was worth it.

I don't know how that engine is set up but the seal is probably to prevent
people from taking more horsepower out of the engine and then claiming that
it didn't last as long as it should. If you are out of guarantee, I would
do what it says in the manual but very carefully. Now those EGT probes we
were talking about would be useful. I'd want to find out a lot more before
I started fiddling with it though. If you do start turning things, put some
scratch marks on the existing position so you have a reference point.

BTW once you are sure both engines are running right and your tachs are
accurate, if you still have a different fuel burn on each side, try running
under power with your centerboards down for a while and see if the fuel burn
evens out at least partially. I'll explain later.

--
Roger Long

[t***@gmail.com]

... I'll explain later. ...

Hmm... I have my suspicions on why that might help, but I'll wait
'till later... :) Anyway, thanks for that and the link. I'll check
it out.

-- Tom.

[Bruce in Bangkok]

Post by t***@gmail.com
I've got a Yanmar 2gm20 that I'm pretty convinced has a problem with
the governor (speed is not well controlled especially when it comes
under load). The seemingly easy path is to fiddle with the injection
limiter. However, there are a couple of things holding me back.
First, they put a wire seal on the adjuster back at the factory. I've
had the problem from day one so I suspect that they didn't get the
adjustment right, but still I figure they sealed it for a reason. I'm
no Japanese scholar but it may even say "Tom, keep your **** hands off
this!" So, will really bad things happen if I mess with the limiter?
Second, I'm not sure exactly how to go about making the adjustment
should I care to. The manual says "if the engine does not accelerate
smoothly turn the limiter slightly counter-clockwise." Good, that's
my problem. The drawing shows a cap nut, lock nut and injection
control shaft. I presume I have to remove the nuts and back the
injection control shaft off a fraction. But, the drawing doesn't show
a slot or anything on the control shaft to keep it from turning while
I move the nuts. Is there some trick to making this work I should know
about when I attempt this? It'd be really nice if I could mark things
so I could at least get back to the current settings if fiddling
doesn't fix things. But how? Thanks!
-- Tom.

First, yes, fiddling with the governor can cause the engine to
explode.

The seals were put on the governor for a reason.

It is doubtful that the factory adjusted the governor incorrectly..

I suggest that you first adjust the idle speed to about 900-1000 RPM
in neutral and check that the high speed RPM is 3600 RPM in neutral.

Once you get these settings made does the engine seem to run normally?

If so, try the same settings with the transmission in forward. Your
idle speed should be essentially the same but high RPM may be a few
hundred RPM lower. If you can't reach full RPM and you have black
smoke coming out the exhaust then your prop is too big. If you can't
reach full RPM and no black smoke then you may have clogged filters -
change them all and try again.

If this doesn't cure your problem then frankly (and not to make fun of
you) from your questions I would suggest that you would be advised to
get a proper mechanic to have a look at things.

Bruce-in-Bangkok
(correct email address for reply)

[t***@gmail.com]

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.

What? It doesn't mention anything like that in the manual (and the
manual does have many warnings in it). It suggests that I might get
black smoke if I overdo it and low torque if I underdo it. Expode?
Really?

Post by Bruce in Bangkok
I suggest that you first adjust the idle speed to about 900-1000 RPM
in neutral and check that the high speed RPM is 3600 RPM in neutral.

Yes. These are correct in the no-load condition.

Post by Bruce in Bangkok
... you may have clogged filters -
change them all and try again.

It is not a filter problem.

Post by Bruce in Bangkok
If this doesn't cure your problem then frankly (and not to make fun of
you) from your questions I would suggest that you would be advised to
get a proper mechanic to have a look at things.

No problem. I'm not proud, but I've done this to no avail. I've had
four mechanics go over it and none of them have been able to fix the
problem. The last time I hauled the boat I pulled the motor and sent
it to the dealer and they couldn't fix it. If you can recommend a
competent mechanic who will come down to my boat here in Hawaii,
great. The timing is good, the injectors are good, the fuel system is
good as far as the injector pump. I could pull the injector pump off
and take it to a shop for a rebuild, but that involves hauling the
boat as there's no way to do that without pulling the engine and no
space to do that without pulling the sail-drive and that causes the
boat to sink if you do it in the water... It is something I can work
around (I've been doing so for years), but it annoys me. Are you sure
I'm going to blow up the engine if I mess with the limiter? It's so
tempting and the manual certainly suggests that it is a reasonable
place to look for the problem, but blowing up is a bit too much down
side for me...

-- Tom.

[Bruce in Bangkok]

Post by t***@gmail.com

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.

What? It doesn't mention anything like that in the manual (and the
manual does have many warnings in it). It suggests that I might get
black smoke if I overdo it and low torque if I underdo it. Expode?
Really?

If you were to tinker with the governor sufficiently it could cause
the engine to "run away", i.e., to run at continuously increasing RPM
until something (probably a connecting rod) fails, usually knocking
holes in the engine and firing parts around the boat.

I don't mean to imply that it WILL happen but if you aren't aware that
it CAN happen then perhaps you shouldn't be "fixing" it.

Post by t***@gmail.com

Post by Bruce in Bangkok
I suggest that you first adjust the idle speed to about 900-1000 RPM
in neutral and check that the high speed RPM is 3600 RPM in neutral.

Yes. These are correct in the no-load condition.

Post by Bruce in Bangkok
... you may have clogged filters -
change them all and try again.

It is not a filter problem.

Post by Bruce in Bangkok
If this doesn't cure your problem then frankly (and not to make fun of
you) from your questions I would suggest that you would be advised to
get a proper mechanic to have a look at things.

No problem. I'm not proud, but I've done this to no avail. I've had
four mechanics go over it and none of them have been able to fix the
problem. The last time I hauled the boat I pulled the motor and sent
it to the dealer and they couldn't fix it. If you can recommend a
competent mechanic who will come down to my boat here in Hawaii,
great.

Nope! You bring your boat to me here in Thailand :-)

Post by t***@gmail.com
The timing is good, the injectors are good, the fuel system is
good as far as the injector pump. I could pull the injector pump off
and take it to a shop for a rebuild, but that involves hauling the
boat as there's no way to do that without pulling the engine and no
space to do that without pulling the sail-drive and that causes the
boat to sink if you do it in the water... It is something I can work
around (I've been doing so for years), but it annoys me. Are you sure
I'm going to blow up the engine if I mess with the limiter? It's so
tempting and the manual certainly suggests that it is a reasonable
place to look for the problem, but blowing up is a bit too much down
side for me...
-- Tom.

First of all, the word "limiter" is a bit confusing. It may be a
"Yanmar" word but it is not a word normally associated with diesel
engines except in the sense of a RPM limiter which usually implies a
device to limit the maximum RPM - a safety devise in other words -
which is not a part that Yanmar uses on the 2GM20.

A diesel engine usually has two owner adjustable settings. The high
and low RPM settings, usually screw adjustments acting on the fuel
lever. If this is what you are referring to then it is all right to
adjust them but you seem to be saying that both high and low RPM is
correct.

Further, adjusting the stops for the fuel lever won't effect anything
except the RPM settings because there is no direct connection between
the fuel lever and the injection pump. It only compresses a spring
that works against the governor.

Can you give a better description of the problem? For example, does
the engine accelerate normally when in neutral? Does the engine run
rough while accelerating? Does it only happen with the engine in
forward or reverse? Does the engine vibrate more then normal when it
is doing whatever it is doing? Are you jamming the throttle from idle
to wide open very rapidly? Upon acceleration does the engine
momentarily over speed and then settle back to the selected RPM?

Bruce-in-Bangkok
(correct email address for reply)

[t***@gmail.com]

... First of all, the word "limiter" is a bit confusing. It may be a
"Yanmar" word but it is not a word normally associated with diesel
engines except in the sense of a RPM limiter which usually implies a
device to limit the maximum RPM - a safety devise in other words -
which is not a part that Yanmar uses on the 2GM20.

Well, I'm not even to the point where I can pretend to be clued in
here so I'm just using the terminology out of the manual. The
governor has three externally adjustable controls: "Injection
Limiter", "no-load maximum speed limiter", and "idling adjuster". I'm
familiar with the idling adjuster and it's trivial to work with. The
no-load maximum speed limiter is sealed at the factory and seems to be
correct. So, I'm thinking of messing with the injection limiter. It
is essentially the end stop for the fuel control lever on the
injection pump and limits the total amount of fuel that the governor
can demand. The manual says " if the engine does not accelerate
smoothly (ie. speed is not well controlled), turn the limiter slightly
counter-clockwise. Note: if it is turned back too much, it will
produce exhaust smoke." Black smoke I can deal with. Thrown rods
would suck. Since they do seal the injection limiter at the factory
I'm taking your warning seriously, but it isn't what I want to
hear...

Further, adjusting the stops for the fuel lever won't effect anything
except the RPM settings because there is no direct connection between
the fuel lever and the injection pump. It only compresses a spring
that works against the governor.

Right, the part I'm looking at prohibits the governor from opening the
fuel pump beyond a certain point (a slightly fuzzy point as it has a
spring in it too). It is not a speed control at all.

Can you give a better description of the problem? For example, does
the engine accelerate normally when in neutral?

Generally, yes, though when the high output alternator kicks with a
big load the engine falls back to idle speed.

Does the engine run
rough while accelerating?

No, it runs very smoothly.

Does it only happen with the engine in
forward or reverse?

Both and neutral.

Does the engine vibrate more then normal when it
is doing whatever it is doing?

No.

Are you jamming the throttle from idle
to wide open very rapidly?

No, and if demand comes onto the engine when it is stable in high idle
it will loose rpms.

Upon acceleration does the engine
momentarily over speed and then settle back to the selected RPM?

No, never. Indeed, it tends to not reach speed so that I have to over
throttle a bit to get the desired rpms and then back down to keep them
steady. It is not lash in the morse cable.

The problem seems most marked when the motor is cold, but as the
batteries demand drops I'm asking the engine to produce less torque
after it has run for a while and even when the batteries are topped
off it still tends not to reach the demanded rpms. I have noticed
that this engine uses less fuel than its counterpart when running at
speed even when the nominal rpms are even. I am certainly confused.
But like I say I've had the pros go over it and they've been unable to
fix it. We've gone over the fuel system multiple times except that I
haven't had the injection pump out and I haven't messed with the
injection limiter. It may be that the injection pump is mis-shimmed
and thus the timing is out but getting the pump off is a major PIA
with this installation. The limiter I can get at so it tempts me...

-- Tom.

[t***@gmail.com]

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.

Just to make sure we're on the same page, I'm not planning on messing
with the no-load maximum speed limiter. That's just fine and the
manual says, more or less, don't mess. I'm looking at the injection
limiter which is also sealed but which shouldn't change the ultimate
rpms and which the manual provides a method for adjusting... No, no,
don't hold back, I can take it :) Really, thanks for the input.

-- Tom.

[Bruce in Bangkok]

Post by t***@gmail.com

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.

Just to make sure we're on the same page, I'm not planning on messing
with the no-load maximum speed limiter. That's just fine and the
manual says, more or less, don't mess. I'm looking at the injection
limiter which is also sealed but which shouldn't change the ultimate
rpms and which the manual provides a method for adjusting... No, no,
don't hold back, I can take it :) Really, thanks for the input.
-- Tom.

I finally located a 2GM20 manual. downloaded it from
http://motoren.ath.cx/menus/yanmar.html
and "limiter" IS a "anmar"word.

The Manual quite emphatically states that the high speed adjustment
and the Fuel Injection Limiter should not be adjusted and will void
the guarantee if the seal is broken.

The screw labeled "No Load Maximum Speed Limiter" adjusts the linkage
to adjust the high RPM. The "Fuel injection Limiter" acts as a stop to
limit the maximum movement of the fork that moves the fuel rack that
determines how much fuel the individual injection pumps inject.

If, for example, the engine is idling and you jam the throttle full
open the Speed Control Lever applies force to the Governor Spring
which forces the Governor Lever to pull the rack (in the injection
pump) to the high fuel position and feeding more fuel to the engine
which causes the engine to accelerate. When the engine RPM reaches the
speed dictated by the tension of the Governor Spring the Governor
Weights swing outward and force the Governor Lever back against the
force of the Governor Spring to maintain the RPM selected by the
position of the Fuel Control Lever acting through the Governor Spring.

However, prior to the Governor Weights opening there is nothing to
resist the pull of the Governor Spring so the "Fuel Injection Limiter"
comes into play and acts as a stop to limit maximum movement of the
Governor Lever before the engine accelerates to a speed sufficient to
actuate the Governor Weights.

I'm not sure whether the Fuel Injection Limiter has a spring loaded
plunger in it or not. Detroit Diesel engines had a similar device but
in their case it was to limit surge at idle.

Backing the Fuel Injection Limiter out will increase amount of fuel
during acceleration before the Governor Weights have a chance to react
and thus the chance of over revving the engine is increased. Screwing
it in will reduce the amount of fuel and the engine will accelerate
slower then normal.

I'm certainly not going to recommend that you violate the
manufacturer's recommendations but if you are committed then hold the
safety wired nut and remove the acorn nut. The screw should have a
slot so it can be adjusted with a screw driver, if not scratch a line
on the screw so you can tell how far you have turned it.

First of all, with the boat securely tied to the dock (you don't
want to be charging all over the ocean while you are trying to adjust
the engine) try moving the throttle rapidly from idle to about half
throttle, with the transmission in neutral. You should get a puff of
black smoke and the engine should smoothly accelerate to whatever
speed your throttle is set to.

Backing the Fuel Injection Limiter out will increase the amount of
fuel available for acceleration and therefore a bigger puff of black
smoke.

Turning the screw in will reduce the amount of fuel available for
acceleration and reduce the puff of black smoke.

A normally operating diesel engine always has a little black smoke
when it accelerates.

If you reach a point that the engine accelerates to a higher RPM and
then settles back to a lower speed you have gone too far. Screw the
Fuel Injection Limiter back in a bit.

I would suggest moving the screw not more then a quarter turn at a
time.

Once things seem to work correctly try the same thing with the
transmission in gear and make any necessary adjustment.

Once you have the engine running properly when you accelerate to half
throttle try idle to full throttle (carefully). Once you have the idle
to full throttle acceleration adjusted both in neutral and in gear you
should have the engine correctly adjusted.


Bruce-in-Bangkok
(correct email address for reply)

[t***@gmail.com]

Post by Bruce in Bangkok
The Manual quite emphatically states that the high speed adjustment
and the Fuel Injection Limiter should not be adjusted and will void
the guarantee if the seal is broken.

Oddly enough my manual doesn't say that for the injection limiter but
does for the no-load... But I'm sure you're right, why else would
they seal it?

Post by Bruce in Bangkok
I'm not sure whether the Fuel Injection Limiter has a spring loaded
plunger in it or not. Detroit Diesel engines had a similar device but
in their case it was to limit surge at idle.

Yes, the manual shows a spring in it (though the manual isn't always a
perfect indicator of what is actually installed).

Post by Bruce in Bangkok
.. The screw should have a
slot so it can be adjusted with a screw driver, if not scratch a line
on the screw so you can tell how far you have turned it.

Right, in practice the nuts and washers are all tight against each
other and no part of the shaft is showing. The adjuster is a hollow
threaded rod with a spring inside of it. The slot on the top of the
rod is the spring retention screw. Not sure if turning it ccw will
undo it or the control shaft. Assuming nothing moves when I take the
acorn I suppose I could make a mark on the shaft w/respect to the lock
nut.

Thanks!

-- Tom.

[Bruce in Bangkok]

Post by t***@gmail.com

Post by Bruce in Bangkok
The Manual quite emphatically states that the high speed adjustment
and the Fuel Injection Limiter should not be adjusted and will void
the guarantee if the seal is broken.

Oddly enough my manual doesn't say that for the injection limiter but
does for the no-load... But I'm sure you're right, why else would
they seal it?

Post by Bruce in Bangkok
I'm not sure whether the Fuel Injection Limiter has a spring loaded
plunger in it or not. Detroit Diesel engines had a similar device but
in their case it was to limit surge at idle.

Yes, the manual shows a spring in it (though the manual isn't always a
perfect indicator of what is actually installed).

Post by Bruce in Bangkok
.. The screw should have a
slot so it can be adjusted with a screw driver, if not scratch a line
on the screw so you can tell how far you have turned it.

Right, in practice the nuts and washers are all tight against each
other and no part of the shaft is showing. The adjuster is a hollow
threaded rod with a spring inside of it. The slot on the top of the
rod is the spring retention screw. Not sure if turning it ccw will
undo it or the control shaft. Assuming nothing moves when I take the
acorn I suppose I could make a mark on the shaft w/respect to the lock
nut.
Thanks!
-- Tom.

Update:

When I said to hold the nut when removing the acorn nut I neglected to
say"loosen the nut when adjusting the screw".

Let us know how it works out.

Bruce-in-Bangkok
(correct email address for reply)

[t***@gmail.com]

... When I said to hold the nut when removing the acorn nut I neglected to
say"loosen the nut when adjusting the screw". ...

Thanks, Bruce. I'll certainly report back if I go for it and I don't
blow myself up...

-- Tom.

[Roger Long]

You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?

I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react. The weights stick slightly and then let go.
Increasing the rate at which fuel flow can be increased during accelleration
might compensate but, if this is the case, could lead to further instability
because of "overshoot" when the governor weights unstick.

It also sounds like you might have too large an alternator. Prop demand
won't, or shouldn't, change suddenly but a sudden load like a large
alternator on a small engine like this may simply be outside the design
envelope of the fuel control system. Actually, it is probably right on the
edge so one engine is OK and the other has problems. This whole
installation was about 30 feet long so it was pretty impressive.

Here's my governor sea story:

I worked on the repowering of a large oceanographic vessel. We installed
two EMD engines (same as in railroad locomotives) that had been in a
government warehouse since about WWII. Each gearbox had a shaft running
back to DC drive motors taken out of an older diesel electric vessel and
converted into generators to run the ship's bow thruster. These motors were
about 5 feet in diameter and I put a big flexible coupling on the front of
the generators that was like half of a car tire bolted to a big metal disc.

When we first fired up the engines, one ran fine. The other began surging
and lunging back and forth as soon as the generator was clutched in with
such violence that we could see the generator beds and ship structure flex.
It was astounding and alarming during the second or two it took to grab the
PTO handle back into OFF. The whole installation was about 30 feet long so
it was pretty impressive. Both were identical so it was a real mystery.

They called in an EMD expert from Texas who flew up. We stated up the
engine, clutched it in, watched the lunging for 2 seconds and shut down.
The expert hopped up on the engine, took the cover off the governor and
said, "Get me a drill with a 3/16" bit." He drilled a hole in something,
fiddled around for about 10 seconds, put the top back on, and started to
leave. We asked if he wanted to see it run and he said, no, he knew it
would work. It did. He was on the ship for about 20 minutes.

It turned out that one engine had a marine governor and the other a railroad
locomotive governor. The railroad governor had a second set of weights
that, when sudden load was put on the engine, would rapidly increase the
fuel flow. This was so the engine wouldn't bog down when the slack came out
of the couplers of the railroad cars. When we clutched in the PTO, the
rubber tire flex coupling would wind up as. The load would cause the
governor to goose the engine and the timing was such that the unwinding of
the flex coupling would exactly match up with the time it took for the
governor to react. The impulse went back and forth magnifying each time
like a huge mechanical laser. All the fellow from Texas did was drill a
hole in the two discs that held the two sets of weights and insert a pin to
disable the goosing function.

--
Roger Long

[Bruce in Bangkok]

On Fri, 21 Mar 2008 07:51:59 -0400, "Roger Long"

Post by Roger Long
You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?
I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react. The weights stick slightly and then let go.
Increasing the rate at which fuel flow can be increased during accelleration
might compensate but, if this is the case, could lead to further instability
because of "overshoot" when the governor weights unstick.
It also sounds like you might have too large an alternator. Prop demand
won't, or shouldn't, change suddenly but a sudden load like a large
alternator on a small engine like this may simply be outside the design
envelope of the fuel control system. Actually, it is probably right on the
edge so one engine is OK and the other has problems. This whole
installation was about 30 feet long so it was pretty impressive.
I worked on the repowering of a large oceanographic vessel. We installed
two EMD engines (same as in railroad locomotives) that had been in a
government warehouse since about WWII. Each gearbox had a shaft running
back to DC drive motors taken out of an older diesel electric vessel and
converted into generators to run the ship's bow thruster. These motors were
about 5 feet in diameter and I put a big flexible coupling on the front of
the generators that was like half of a car tire bolted to a big metal disc.
When we first fired up the engines, one ran fine. The other began surging
and lunging back and forth as soon as the generator was clutched in with
such violence that we could see the generator beds and ship structure flex.
It was astounding and alarming during the second or two it took to grab the
PTO handle back into OFF. The whole installation was about 30 feet long so
it was pretty impressive. Both were identical so it was a real mystery.
They called in an EMD expert from Texas who flew up. We stated up the
engine, clutched it in, watched the lunging for 2 seconds and shut down.
The expert hopped up on the engine, took the cover off the governor and
said, "Get me a drill with a 3/16" bit." He drilled a hole in something,
fiddled around for about 10 seconds, put the top back on, and started to
leave. We asked if he wanted to see it run and he said, no, he knew it
would work. It did. He was on the ship for about 20 minutes.
It turned out that one engine had a marine governor and the other a railroad
locomotive governor. The railroad governor had a second set of weights
that, when sudden load was put on the engine, would rapidly increase the
fuel flow. This was so the engine wouldn't bog down when the slack came out
of the couplers of the railroad cars. When we clutched in the PTO, the
rubber tire flex coupling would wind up as. The load would cause the
governor to goose the engine and the timing was such that the unwinding of
the flex coupling would exactly match up with the time it took for the
governor to react. The impulse went back and forth magnifying each time
like a huge mechanical laser. All the fellow from Texas did was drill a
hole in the two discs that held the two sets of weights and insert a pin to
disable the goosing function.

You flew him in from Texas?

Good Lord I must be getting old. EMD guys used to be all over the
place. A very common engine at one time, We had a whole generator
house full of them at one time in Irian Jaya.

Then the company decided to modernize and sold all the old engines and
replaced them with turbines. do you have any idea how fast the shut
downs work on a turbine?

Once they got the new plant set up the entire site used to go down
several times a day. One turbine would hiccup and go off line. The
remaining units would sense an overload and Bam they would all shut
down.

That story makes me wonder, do any of the smaller commercial vessels
use turbines?




Bruce-in-Bangkok
(correct email address for reply)

[t***@gmail.com]

Post by Roger Long
You say that mechanics have not been able to fix the problem. Are you sure
they did not try these adjustments?

Well, the last folks had the engine for over a month and might have
fiddled with it, but I don' think they did. 100% or respondents say
"fuel restriction or air in fuel" when I describe the problem, but so
far the ones who've attempted to fix it have failed. All the obvious
things have been done multiple times.

Post by Roger Long
I'm beginning to suspect that you have a problem inside the governor itself,
corrosion, debris, slight manufacturing defect or tolerance drift is making
it sluggish to react.

Yes, that could be the case. As Bruce has pointed out these are well
made engines and it would be a rare affliction, but basically all
that's left unchecked is the governor and its adjustments and the
injection pump. Also, the fact that there seems to be a change when
the engine warms up seems suggest to me that there might be a change
in tolerances w/in the gov mechanism itself... And, makes the
injection limiter a less likely culprit. The injection limiter is a
bit of a hail Mary, but seems easy...

Post by Roger Long
It also sounds like you might have too large an alternator.

In practice there's no doubt that the alternator is too large for that
engine. But, the identical machine works on the left side...

-- Tom.

[Roger Long]

Post by t***@gmail.com
In practice there's no doubt that the alternator is too large for that
engine. But, the identical machine works on the left side...

You might try swapping the alternators (and voltage regulators if separate)
from side to side. It could be that the governors are right on the edge of
not being able to cope with the electric loads and there is a difference in
how the alternators are functioning. Is there a difference in electric
loads on the engines, say a fridge being driven from one?

Just out of curiosity, how many hours on these engines?

--
Roger Long

[t***@gmail.com]

Post by Roger Long
You might try swapping the alternators (and voltage regulators if separate)
from side to side. It could be that the governors are right on the edge of
not being able to cope with the electric loads and there is a difference in
how the alternators are functioning.

That's an interesting thought. Both are controlled by my Ample Power
controller and share the same loads (at least in theory). The port
engine seem quite cheerful with its load (good throttle response, no
smoke, smooth running). The starboard engine loses power but doesn't
smoke or run rough when asked to do the same task. I have had the stb
alternator rebuilt and that didn't change anything.

Post by Roger Long
Just out of curiosity, how many hours on these engines?

1,338.5 port and 1,354.8 stb.

-- Tom.

[Roger Long]

Hey Tom, I remembered to bring the service manual for my 2Q (yes that's a
"Q") M20 back from the boat today. Assuming that they didn't reinvent the
wheel when they went to the GM series and your manual is as complete as
mine, there is a gold mine of information there.

Can you email me a scan or digital photo showing the basic governer drawing
from your manual? I just want to be sure the basic design was not changed
too much.

Everything in the QM, and I strongly suspect on your GM as well, depends on
balances of spring pressure and there are numerous points where a bit of
corrosion, burr left over from manufacturing, etc. could create exactly the
symptoms you describe. All of the regulation of the amount of fuel
delivered to the cylinder is via a single lever to the injection pump. The
only effect of fiddling with any part of the governer is to move this lever
too far for the RPM the engine is operating at.

Sudden loads, such as your oversize alternator, compress the spring inside
the engine, the tension of which is controlled by the nut you are
considering turning. The prime suspect in my mind right now is that amount
of sudden load thrown on the engine by your alternator has either weakened
or perhaps even cracked this spring. This is a funky enough analogue system
that the parts could be perfectly OK but natural variation is enough for one
engine to have a problem.

You probably need to have the back cover taken off this engine and
everything in the governor system checked out. It doesn't look like rocket
science.

I spent a fascinating half hour learning how this mysterious little beast
works. I've just started. Send me that page if you can. I'm pretty sure
we'll find that these are similar enough that we can figure it out.

--
Roger Long

[t***@gmail.com]

... Everything in the QM, and I strongly suspect on your GM as well, depends on
balances of spring pressure and there are numerous points where a bit of
corrosion, burr left over from manufacturing, etc. could create exactly the
symptoms you describe.

Yes that sounds like the same beast. I've sent you a few scans. Hope
they aren't to horrible.

You probably need to have the back cover taken off this engine and
everything in the governor system checked out. It doesn't look like rocket
science.

Yes, but it is a PIA. Actually, I was just looking at the injector
pump and I think I can get it out of there (I'll have to rescue the
shims by feel, but... So, I might pull it and have it over to the
shop before I have the front of the engine off. Still, turning one
little screw sounds soooo much easier... :)

Cheers,

-- Tom.

[Roger Long]

Got the scans. Unfortuantely, it is a very different design so I can't help
you much from my engine's manual. The basic principles are the same though.
There is a lot that can go subtly wrong in there that could cause exactly
the symptoms you are experiencing.

--
Roger Long

[Jere Lull]

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.
The seals were put on the governor for a reason.
It is doubtful that the factory adjusted the governor incorrectly..
I suggest that you first adjust the idle speed to about 900-1000 RPM
in neutral and check that the high speed RPM is 3600 RPM in neutral.
Once you get these settings made does the engine seem to run normally?
If so, try the same settings with the transmission in forward. Your
idle speed should be essentially the same but high RPM may be a few
hundred RPM lower. If you can't reach full RPM and you have black
smoke coming out the exhaust then your prop is too big. If you can't
reach full RPM and no black smoke then you may have clogged filters -
change them all and try again.
If this doesn't cure your problem then frankly (and not to make fun of
you) from your questions I would suggest that you would be advised to
get a proper mechanic to have a look at things.
Bruce-in-Bangkok
(correct email address for reply)

I usually agree with you, and mostly agree with what I see as your
intentions, but you got some things wrong in my hardly ever humble
opinion....

The factory could well have screwed things up. Their employees have
little if no investment, though my observation has been that they
usually do at least a decent job.

Minimum idle speed on our 2GM20F is set to a bit under 600. We were
warned to long-term idle/charge at about 1200, so that amounts to our
usual idle.

With a properly pitched prop, there is no way we can pull full RPMs at
the dock in forward or reverse. We blow incredible black billows of
smoke trying.

When we open the throttle to full while freely moving, we push past
hull speed, show the max RPMs we pitched for and blow a bit of black
smoke. That IMHO is about the way is should be.

[Bruce in Bangkok]

Post by Jere Lull

Post by Bruce in Bangkok
First, yes, fiddling with the governor can cause the engine to
explode.
The seals were put on the governor for a reason.
It is doubtful that the factory adjusted the governor incorrectly..
I suggest that you first adjust the idle speed to about 900-1000 RPM
in neutral and check that the high speed RPM is 3600 RPM in neutral.
Once you get these settings made does the engine seem to run normally?
If so, try the same settings with the transmission in forward. Your
idle speed should be essentially the same but high RPM may be a few
hundred RPM lower. If you can't reach full RPM and you have black
smoke coming out the exhaust then your prop is too big. If you can't
reach full RPM and no black smoke then you may have clogged filters -
change them all and try again.
If this doesn't cure your problem then frankly (and not to make fun of
you) from your questions I would suggest that you would be advised to
get a proper mechanic to have a look at things.
Bruce-in-Bangkok
(correct email address for reply)

I usually agree with you, and mostly agree with what I see as your
intentions, but you got some things wrong in my hardly ever humble
opinion....
The factory could well have screwed things up. Their employees have
little if no investment, though my observation has been that they
usually do at least a decent job.

Most of the Japanese factories are so automated or use so many jigs
and fixtures that human error is reduced to a minimum. Not to say it
never happens but I think it is rare.

Post by Jere Lull
Minimum idle speed on our 2GM20F is set to a bit under 600. We were
warned to long-term idle/charge at about 1200, so that amounts to our
usual idle.

I know that.. Re read what I wrote. I wanted him to set the idle high
enough that low idle speed wouldn't be a factor. If the thing ran well
with the higher idle it would be easy to reset that later. I probably
should have elaborated on that in the original post.

Post by Jere Lull
With a properly pitched prop, there is no way we can pull full RPMs at
the dock in forward or reverse. We blow incredible black billows of
smoke trying.

Again, I should have been more detailed. If he gets black smoke at
full throttle while under way the prop is too big.

I kow that some people deliberately over prop with the idea that they
get better fuel economy because they are running at a lower RPM but I
didn't want to get into all that.

Post by Jere Lull
When we open the throttle to full while freely moving, we push past
hull speed, show the max RPMs we pitched for and blow a bit of black
smoke. That IMHO is about the way is should be.

Probably in real life that is about the best you can do. theoretically
you should have no black smoke. Big stationary engines are tuned that
way, but with a boat there are just too many variables. going up hill
or down; how dirty is the bottom; full tanks or empty; wind behind or
before.

I made a later post after finally finding a service manual.

I had a 2GM20 at one time and even after running it for a couple of
years I had no idea that it was as sophisticated as it is(for a little
engine, that is).


Bruce-in-Bangkok
(correct email address for reply)

[Jill M]

http://www.alliedkenco.com/catalog/advanced_search_result.php?keywords=inject&osCsid=undefined

[Vic Smith]

Post by t***@gmail.com
I've got a Yanmar 2gm20 that I'm pretty convinced has a problem with
the governor (speed is not well controlled especially when it comes
under load).

You may get more on-target suggestions if you describe the symptoms
more precisely - such as what load, what rpm variations.

--Vic

[t***@gmail.com]

Post by Vic Smith
You may get more on-target suggestions if you describe the symptoms
more precisely - such as what load, what rpm variations.

Could be. :) But in a way I'm trying to avoid doing that because I've
been down that route here and with pros and 100% of people say air in
the fuel. For years I've believed them and labored to get the fuel
system just so and I've spend a lot of money having the pros work it
over, too. It is not a show stopper. I've traveled tens of thousands
of miles with it. But, it is a continual annoyance. So, basically
the last part that nobody has messed with that could reasonably be
causing my problems is the governor. Applying the do the easy stuff
first principle I looked at the beast and it has an adjustment the
might possibly fix or mask the problem and it looks super easy to do.
But, it is factory sealed. So, my question was, in essence, will
vengeful samurai descend from heaven to cause me grave bodily harm if
I tweak that puppy? So far, I think I've gotten a good solid "maybe"
on that. I'm not really asking for a diagnosis of the problem. I
pretty much lost faith in them (though they are always amusing and I'm
happy to read any that are proffered).

-- Tom.

[Roger Long]

I think, that if the limiter spring is not broken and there is nothing that
is preventing the parts associated with the spring from moving freely, it
will probably be OK to adjust it very carefully. I'm concerned about
putting more load on a broken or hung up spring and having the engine seem
to improve but then be responding improperly. Record the position of the
safety wire hole and carefully count and record turns. If it doesn't fix
things, put it back to the present position.

Looking at it is clearly the first thing to do. Look carefully for signs of
rust as well. If it doesn't look like it gets oil from the engine lube
system, put something on it.

Here's another idea:

Video the engine misbehaving. I'll hire half an hour of time from the
mechanic at my boatyard and Yanmar dealer who I think is pretty good and
take the video to show him. You can pay me for his time and I'll assure him
that you've already gotten the fuel system tight, etc.

It might make sense that the engine is using less fuel. Since maximum fuel
usage is during acceleration, the engine may not be accelerating when loads
change and actually saving fuel by coming up to the new load very slowly.
Although it sounds annoying, your boat just slows down slightly and you or
your autopilot add a touch of rudder to maintain course. With fuel prices
what they are, maybe you should find out what is wrong and do it to the
other engine:)

--
Roger Long

[Vic Smith]

Post by t***@gmail.com

Post by Vic Smith
You may get more on-target suggestions if you describe the symptoms
more precisely - such as what load, what rpm variations.

Could be. :) But in a way I'm trying to avoid doing that because I've
been down that route here and with pros and 100% of people say air in
the fuel. For years I've believed them and labored to get the fuel
system just so and I've spend a lot of money having the pros work it
over, too. It is not a show stopper. I've traveled tens of thousands
of miles with it. But, it is a continual annoyance. So, basically
the last part that nobody has messed with that could reasonably be
causing my problems is the governor. Applying the do the easy stuff
first principle I looked at the beast and it has an adjustment the
might possibly fix or mask the problem and it looks super easy to do.
But, it is factory sealed. So, my question was, in essence, will
vengeful samurai descend from heaven to cause me grave bodily harm if
I tweak that puppy? So far, I think I've gotten a good solid "maybe"
on that. I'm not really asking for a diagnosis of the problem. I
pretty much lost faith in them (though they are always amusing and I'm
happy to read any that are proffered).

Know what you mean. The reason I mentioned that is once in an auto
group somebody reported odd but specific symptoms of stalling in his 5
year old supercharged Pontiac. He was getting all kinds of logical -
but wrong - advice from technicians. It just so happened that a
workmate of mine had that exact car and recently related to me those
exact symptoms. His mechanic couldn't solve it and sent it to the
Pontiac dealer, who quickly fixed it.
This posting activity happened on a weekend and I posted that I would
find the solution from my workmate on Monday. But since I ended up
not working that Monday the original poster started e-mailing me.
I called my workmate to look at his dealer receipt when he went home,
and the only part listed was a fuel pump resistor.
When I relayed this to the original poster, he went into his garage
and had the resistor bypassed and on order within an hour, his problem
was gone, and he thanked me heartily. He seemed the type really fond
of his car and wanting to always do his own fixing. As much as I've
worked on cars, the only time I touched a resistor was on my son's
Sony PS1 playstaion. I melted everything into ruination.
But the car problem solution was an unusually fortuitous set of
events, and usenet worked quite well.
Your situation is different of course, and there is a smaller set of
Yanmar owners, but there's always a chance.
Besides, it makes people feel good to make suggestions, no matter
how irrelevant they are (-:

--Vic

[t***@gmail.com]

... Besides, it makes people feel good to make suggestions, no matter

Sorry, I didn't mean to deprive you of you're go. Please, suggest
away! :) I'm planning on taking the boat out in the morning anyway,
so I'll try and pay particular attention to the motor and report some
symptoms for you.

Cheers, and Happy Easter,

-- Tom.

[t***@gmail.com]

... I'm planning on taking the boat out in the morning anyway,
so I'll try and pay particular attention to the motor and report some
symptoms for you. ...

Alright, I took the family out for a cruise yesterday and did keep an
eye on the engines. I reduced the warm up period to about 10 minutes
and the batteries were fully charged when I left the dock. On the run
out of the harbor I set both throttles to about 2300 and for the first
5 minutes or so the stb eng would run up to just under the desired rpm
and then drop off 200 fairly slowly and then run back up. The full
cycle taking about 10 seconds. We set sail and sailed for a couple of
hours and then restarted the motors to anchor and throttle response
appeared normal. After a couple hours at anchor I motored home (about
4 miles). The engines appeared to run normally. Neither smokes at
WOT and both ran up to full rpms (though we were running with a
strongish tail wind). I know this isn't going to help my case as it
sure sounds like air in the fuel. Still, I'm pretty convinced that's
not it. I have spent a lot of time with the fuel system. The filters
are new. The day tank is above the engine. There doesn't appear to
be any water or growth in the fuel. But, I hope everyone who wants to
will feel free to tell me what they think the problem is. Fire
away! :)

-- Tom

PS. And thanks.

[Edgar]

Post by t***@gmail.com

... I'm planning on taking the boat out in the morning anyway,
so I'll try and pay particular attention to the motor and report some
symptoms for you. ...

Alright, I took the family out for a cruise yesterday and did keep an
eye on the engines. I reduced the warm up period to about 10 minutes

<snipped.>

Warming up a diesel for 10 minutes is unnecessarily long and does no good.
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

[Roger Long]

Post by Edgar
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

5 minutes warm up before any load according to the manual for my engines.

I agree thought that excessive idling isn't good. "Reducing to 10 minutes"
sounds like too much to me.

--
Roger Long

[Larry]

Post by Roger Long
I agree thought that excessive idling isn't good. "Reducing to 10
minutes" sounds like too much to me.

Drive by any truck stop at 2AM in the cold. They idle 24/7 and only run 2
million miles between overhauls. What nonsense.

[Gordon]

Post by Larry

Post by Roger Long
I agree thought that excessive idling isn't good. "Reducing to 10
minutes" sounds like too much to me.

Drive by any truck stop at 2AM in the cold. They idle 24/7 and only run 2
million miles between overhauls. What nonsense.

Idling a diesel engine such as in a boat means it will never warm up
to proper operating temperatures thus causing more wear.
In the case of a semi in a truck stop, there is an automatic shutter
in front of the radiator which closes down to keep the idling engine at
operating temps. They don't shut them down because in the morning they
would again be abusing a cold engine.
G

[Larry]

Post by Gordon

Post by Larry

Post by Roger Long
I agree thought that excessive idling isn't good. "Reducing to 10
minutes" sounds like too much to me.

Drive by any truck stop at 2AM in the cold. They idle 24/7 and only
run 2 million miles between overhauls. What nonsense.

Idling a diesel engine such as in a boat means it will never warm up
to proper operating temperatures thus causing more wear.
In the case of a semi in a truck stop, there is an automatic shutter
in front of the radiator which closes down to keep the idling engine
at operating temps. They don't shut them down because in the morning
they would again be abusing a cold engine.
G

There were two 8V92TA train engines in my buddy Dan's 1981 Hatteras 56.
Until I came along, he never operated these monsters at any speed over
half of hull speed because he was terrified of it. We're talking about
YEARS of "just idling around".

The first time I opened the throttles wide as we cleared the Charleston
Jetties, enough carbon black poured out of the pipes to make a mountain
of tires, spread out over miles of ocean as a black cloud! She smoothed
right out after clearing her throat. He went below, convinced the
engines would explode in a blast of parts as she cleared 2/3 of redline.
They didn't....they were fine....albeit a tiny bit noisy because Dan had
the engine room hatches open with his fingers in his ears....(c;

Soon after he spotted the fuel flow meters and did a little math, I
pulled the throttles back to a more economical position, just above
planing speed. What a beautiful yacht she was cruising along, a giant
bassboat.

When he sold her, right after Larry got everything working below the
galley house and engine rooms and electronics suite, the buyer had
General Diesel, our DD shop, to pull them down and inspect them. I knew
he was wasting his money because they cranked so easily I'd be afraid to
jack them over with a big wrench for fear they would spontaneously start
they started so easily...GD found ONE out-of-spec spring in the
starboard engine, in spite of Dan's "trawler speeds" all those years.
They were just fine. I saw her a couple of years later and talked to
the new owner who'd had her in the Caribbean long enough to completely
blister her underwater hull. He cracked an injector, but that was all.
She was still just fine, thousands of hours later.

You yachties need a little reality check. Ask a local shrimper if you
can go out with him for a day and watch his diesel(s) run. Count all
the idling along hours during the day and multiply by the shrimp
season... Notice how his engines are all pampered and pure like yours.

I always thought what killed them first was the water in the injection
system caused by the lazy bastard that owned them NOT filling the tanks
before he stored them and NOT getting the oil changed because "I didn't
run it much". If you crank it full of new oil, a biologic clock starts
ticking as the fuel blowby consumes the lube oil...even if you "don't
run it much". That's what kills sailboat engines.....disuse.

[Gordon]

Post by Larry

Post by Gordon

Post by Larry

Post by Roger Long
I agree thought that excessive idling isn't good. "Reducing to 10
minutes" sounds like too much to me.

Drive by any truck stop at 2AM in the cold. They idle 24/7 and only
run 2 million miles between overhauls. What nonsense.

Idling a diesel engine such as in a boat means it will never warm up
to proper operating temperatures thus causing more wear.
In the case of a semi in a truck stop, there is an automatic shutter
in front of the radiator which closes down to keep the idling engine
at operating temps. They don't shut them down because in the morning
they would again be abusing a cold engine.
G

There were two 8V92TA train engines in my buddy Dan's 1981 Hatteras 56.
Until I came along, he never operated these monsters at any speed over
half of hull speed because he was terrified of it. We're talking about
YEARS of "just idling around".

Sorry Larry but half of hull speed is NOT idling!
Gordon

[Marty]

Post by Gordon

Post by Larry

Post by Roger Long
I agree thought that excessive idling isn't good. "Reducing to 10
minutes" sounds like too much to me.

Drive by any truck stop at 2AM in the cold. They idle 24/7 and only
run 2 million miles between overhauls. What nonsense.

Idling a diesel engine such as in a boat means it will never warm up
to proper operating temperatures thus causing more wear.

Funny, my diesel has a thermostat, runs at the same temp in idle as it
does at full throttle.

Cheers
Marty

[Roger Long]

Post by Marty
Funny, my diesel has a thermostat, runs at the same temp in idle as it
does at full throttle.

That's temperature measured in one spot and will be the same at idle as full
throttle if the cooling system is performing properly. When starting from
cold however, there are variations of temperature all over the engine that
are not measured or directly controlled by a thermostat.

Incidentally, idling an engine that has been run at normal power so that
everything is fully warmed up is probably not nearly as bad for it as
starting it and then running at idle for a couple hours to charge batteries.
Everything is warm and, although it may cool down a bit in some parts, it
won't go through a long period with some parts cold, minimial oil flow, and
no load.

--
Roger Long

[Martin Baxter]

Post by Roger Long

Post by Marty
Funny, my diesel has a thermostat, runs at the same temp in idle as it
does at full throttle.

That's temperature measured in one spot and will be the same at idle as full
throttle if the cooling system is performing properly. When starting from
cold however, there are variations of temperature all over the engine that
are not measured or directly controlled by a thermostat.
Incidentally, idling an engine that has been run at normal power so that
everything is fully warmed up is probably not nearly as bad for it as
starting it and then running at idle for a couple hours to charge batteries.
Everything is warm and, although it may cool down a bit in some parts, it
won't go through a long period with some parts cold, minimial oil flow, and

To be fair, we're probably talking apples and oranges here. My diesel
is a little Volvo D1-13,
http://www.volvo.com/NR/exeres/FD79150C-692D-44D5-A7E5-C4C27D991387.htm

It probably quite quickly comes to the same temperature through out.
When I installed it I went over it with a infrared thermometer and found
very little variation in temp from the bottom of the block to top of the
head, may about 5deg C after 10 minutes of idling.

Cheers
Marty

[Roger Long]

Post by Martin Baxter
When I installed it I went over it with a infrared thermometer and found
very little variation in temp from the bottom of the block to top of the
head, may about 5deg C after 10 minutes of idling.

Hmmm. Nearly even temp after 10 minutes. Maybe that's why 5 minutes is
such a common recommended warm up interval for diesel engines of this class,
close enough to evenly warm but not running excessively at no load.

--
Roger Long

[Marty]

Post by Roger Long

Post by Martin Baxter
When I installed it I went over it with a infrared thermometer and
found very little variation in temp from the bottom of the block to
top of the head, may about 5deg C after 10 minutes of idling.

Hmmm. Nearly even temp after 10 minutes. Maybe that's why 5 minutes is
such a common recommended warm up interval for diesel engines of this
class, close enough to evenly warm but not running excessively at no load.

Indeed, but Volvo says nothing about not running for extended periods at
idle. They do seem to almost brag about how much charging current one
gets from thier souped up alternator at idle.

Cheers
Marty

[Roger Long]

Post by Marty
Indeed, but Volvo says nothing about not running for extended periods at
idle. They do seem to almost brag about how much charging current one
gets from thier souped up alternator at idle.

Could be marketing or it could be that the engine was designed and set up to
be more tolerant of idling than most small marine diesels which were
developed before electrical loads on small craft were anything like what is
common today.

--
Roger Long

[Martin Baxter]

Post by Roger Long

Post by Marty
Indeed, but Volvo says nothing about not running for extended periods at
idle. They do seem to almost brag about how much charging current one
gets from thier souped up alternator at idle.

Could be marketing or it could be that the engine was designed and set up to
be more tolerant of idling than most small marine diesels which were
developed before electrical loads on small craft were anything like what is
common today.

The latter makes sense, the design is quite new and the advertising
specifically mentions todays higher electrical loads. The motor's
emissions meet or exceed EU and California Standards. I only installed
it last fall, put maybe 4 hrs on it before winter lay-up. It does beat
the tar out of the old single cylinder Yanmar, smoother, quieter, more
powerful, yet I think easier on fuel.


Cheers
Marty

[Roger Long]

Ah, emissions. By the time they have designed an engine to meet those
requirements, it will be vastly more sophisticated than the previous
generation of engines. If it is anything like the situation with large
marine diesels, it will be able to idle, at least high idle, for long
periods with no significant problems.

--
Roger Long

[Roger Long]

"Larry" <***@home.com> wrote

(about truck engines again)

Those engine operate in a very different environment. Almost exactly half
of those mile are downhill. If trucks spent 90% of their time going up hill
in low gear which is the kind of loads marine engines experience, the
picture might be very different. Besides, we don't know how much longer
those truck engines would run if they didn't idle them all night. The fact
that they do doesn't prove it is better for the engines, maybe just that
truckers don't like to sit in a cold truck for half an hour in the morning
listening to country music. Besides, those engines are set up with the
expectation of long idle periods which marine engines are not. They have
radiator flaps, different cooling systems, etc.

There was an article about high diesel fuel costs in the paper a couple days
ago and a trucker was complaining about the mileage on his rig. Turns out
to be the same as the mileage my 32 foot boat gets with about 1/20 the
horsepower. That will give you an idea how valid a comparison of marine and
road miles are.

You are right though that idling is not instant death to an engine. My
research vessels spend about half their time at idle which is one of the
reasons I was an early adopter or electronically controlled engines but
ORV's were doing it long before those engines came on the market. Still, if
you have a sailboat and use your engine primarily to charge batteries and
bump you in and out of a small harbor for daysails, a very common service
profile up here, you *may* have problems earlier than you would.

--
Roger Long

[t***@gmail.com]

Post by Edgar
Warming up a diesel for 10 minutes is unnecessarily long and does no good.
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

Help me out, how does it cause wear? Sure, I don't know squat about
engines but it from book learning and a tiny bit of expericene:
Assuming that the oil is of a suitable weight it should work just fine
at idle. The manual requires racing the engine periodically if
running at low speeds for over 2 hours but requires not less than 5
minutes of warm up before _any_ load is applied. Letting the oil
splash about and passing it through the filter once or twice before
things get really hot seems like a good thing to me. The motor is a
bigish chunk of metal and gaskets and spings and such and heating it
up fast must cause stress. I've had the exhaust elbows off both
engines twice and there was no evidence of unusual coking. FWIW, I
generally push the idle speed up during the warm up and have some
alternator load so the motors aren't likely to be running way under
temp anyway.

-- Tom.

[Edgar]

Post by t***@gmail.com

Post by Edgar
Warming up a diesel for 10 minutes is unnecessarily long and does no good.
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

Help me out, how does it cause wear? Sure, I don't know squat about
Assuming that the oil is of a suitable weight it should work just fine
at idle. The manual requires racing the engine periodically if
running at low speeds for over 2 hours but requires not less than 5
minutes of warm up before _any_ load is applied. Letting the oil
splash about and passing it through the filter once or twice before
things get really hot seems like a good thing to me. The motor is a
bigish chunk of metal and gaskets and spings and such and heating it
up fast must cause stress. I've had the exhaust elbows off both
engines twice and there was no evidence of unusual coking. FWIW, I
generally push the idle speed up during the warm up and have some
alternator load so the motors aren't likely to be running way under
temp anyway.
-- Tom.

When the cylinder walls are cold acidic combustion products stay on the
cylinder wall instead of leaving as vapours with the exhaust gases and this
leads to increased wear. Maximum wear occurs near top dead centre when the
piston is slowing and reversing its motion because this is the area where
there is least oil film and the slow motion of the piston rings does not
prevent some metal to metal contact. Lower down the cylinder the piston
rings are riding on an oil film and wear is much lower.
Idling for 5 minutes is not as good for warming up the engine as getting
some load on within, say, 2 minutes. The bit about 'racing' the engine after
prolonged idling is to get some fuel through the injectors as the flow at
idling is so small that the fuel in the injector can start to polymerise and
clog the holes in the nozzle. Here again running at speed with some load on
is better than 'racing' the engine if by racing you mean running up to full
speed on no load.
I accept that your alternator will provide some load but whether this is
enough to be effective depends on the size of the alternator relative to the
power of the engine and whether the alternator finds a battery that is
already fully charged or one that is low and needs some charge.

[t***@gmail.com]

Post by Edgar
When the cylinder walls are cold acidic combustion products stay on the
cylinder wall instead of leaving as vapours with the exhaust gases and this
leads to increased wear.

This I did not know.

Post by Edgar
Idling for 5 minutes is not as good for warming up the engine as getting
some load on within, say, 2 minutes.

The manual is pretty specific. I wonder if there is a trade off that
depends somewhat on the engine involved.

Post by Edgar
The bit about 'racing' the engine after
prolonged idling is to get some fuel through the injectors as the flow at
idling is so small that the fuel in the injector can start to polymerise and
clog the holes in the nozzle.

"This is done to clean out carbon from the cylinder and the fuel
injection valve." Is what they say and I think that means what you
said. :)

Thanks,

-- Tom.

[Roger Long]

This is where the objective of operating manuals diverges from engineering.
The manual is written for a lowest denominator of operator and to cover a
lot of situations in a few words. Thus, "No load until after 5 minutes warm
up." This doesn't mean that getting some load on the engine sooner isn't
slightly better for it.

The first engagement of a marine engine on a docked boat is often a fairly
heavy load. In those circumstances, I warm up the full five minutes
accepting a bit of the extra wear Edgar speaks of as a trade off for other
strains on the engine trying to produce backing out and maneuvering power
before the engine is at minimum proper operating temperature. Starting
underway when striking sails, I'll often put it into gear after just a
minute or two at high idle and very slowly bring up the power over a period
of minutes.

You'll never notice the difference in maintenance and longevity or other
problems of idling your engine on start up for 10 - 20 minutes. It's
probably doing more harm than good but only a very small amount. But, at
today's fuel prices especially, why bother? If you had a whole fleet of
boats, good operating records, and could sort out the noise of individual
engine variation in the data, you probably could detect a small difference
in time between overhauls for long and short warm up periods.

When you get to sailboat engines that are idled for hours a day to run
refrigerators and may sail enough that these periods account for a
significant portion of the operating time, then problems start to show up
that people sometimes notice.

--
Roger Long

[Roger Long]

This now sounds like governer hunting, usually caused by wear or some other
fault in the governor mechanism. It's similar in dynamics to auto pilot
hunting in which some boats steer a slightly "S" course instead of a
straight line.

Did you try www.boatdiesel.com?

--
Roger Long

[t***@gmail.com]

Did you trywww.boatdiesel.com?

Yes, thanks. There were a couple of questions that sounded
interesting but I wasn't able to read any of the replies w/o forking
over $25. I just hate the idea of sending them my credit card info
and having them say "check your fuel lines"...

-- Tom.

[Wayne.B]

Post by t***@gmail.com
Yes, thanks. There were a couple of questions that sounded
interesting but I wasn't able to read any of the replies w/o forking
over $25. I just hate the idea of sending them my credit card info
and having them say "check your fuel lines"...

It's a good forum, lots of experts. Somewhere along the line you will
get your $25 worth.

I believe the classic way of checking for air leaks is to insert a
piece of clear plastic tubing in the fuel feed just before the
injection pump and watch for bubbles.

[Roger Long]

Tom,

The engine that burns more fuel is the one with the control problem, right?

I think the spring in the injection limiter might be weak, broken, or have
some other defect. There could also be excess friction on the shaft the
mechanism that engages the spring runs on. Turning the adjustment could
cause even more problems if so.

If this is the engine that is burning less fuel, I'll rethink but this
device is appears to function like a shock absorber in the system to prevent
brief pulses of fuel when the engine suddenly slows down. It doesn't
directly control the amount of fuel that can be delivered but introduces
some lag and buffering into the linkage that controls the injector pump. If
it is not functioning properly, the result will be much as your car behaves
with a bad shock. It still sits level when still but the wheel with the bad
shock moves up and down wildly when it hits a bump. Does that sound similar
to what you are experiencing? These pulses of fuel, more than the engine can
burn with the available air, could account for your excess fuel burn.

Get an opinion from someone who actually knows but I'll bet a six pack they
are going to tell you they need to pull the rear case cover and look at that
spring.

--
Roger Long

[Roger Long]

Say, I just discovered that there is a plate that allows access to the
injector limit spring and mechanism on my engine without having to pull the
whole rear cover off. Take a look at your engine, I'll bet it has something
similar.

If so, you're in luck having a cat. You can look at both engines and
compare what you see and feel.

--
Roger Long

[t***@gmail.com]

Post by Roger Long
Say, I just discovered that there is a plate that allows access to the
injector limit spring and mechanism on my engine without having to pull the
whole rear cover off. Take a look at your engine, I'll bet it has something
similar.

Yes, it looks like I can remove the idle adjuster assy and get a look
in there (well, feel in there really). I like that idea as I should
be able to slip a feeler or something between the injection limiter
and the crank arm to see that its spring is working and scope out the
regulator springs, too. Cool. Monday, though.

-- Tom.

[t***@gmail.com]

Post by Roger Long
Say, I just discovered that there is a plate that allows access to the
injector limit spring and mechanism on my engine without having to pull the
whole rear cover off. Take a look at your engine, I'll bet it has something
similar.

Ok, I just pulled the cover off. In as much as I can see anything it
all looks fine. The hole is a lot smaller than it looks on the
drawings... The little spring loaded rod that comes out of the limiter
follows the throttle crank through its entire motion and appears to
operate smoothly. I can't really see all the springs towards the
tranny end of the motor but they are there. The whole assy is nicely
oiled and looks lovely. I did tear the gasket while removing the
plate. Any thoughts on whether I need to order the Yanmar part or if
I can get away with some other method (eg. goo or paper)?

I pondered the injection limiter and I can't see any way to fiddle w/
it w/o breaking the seal. Unlike the drawings the seal is through the
cap nut rather than the lock nut... Hmmmm....

-- Tom.

[t***@gmail.com]

Post by t***@gmail.com
I did tear the gasket while removing the
plate. Any thoughts on whether I need to order the Yanmar part or if
I can get away with some other method (eg. goo or paper)?

The local dealer has them in stock for $1.50... So, I'll get a new
Yanmar (tm) one.

-- Tom.

[t***@gmail.com]

Post by t***@gmail.com

Post by t***@gmail.com
I did tear the gasket while removing the
plate. Any thoughts on whether I need to order the Yanmar part or if
I can get away with some other method (eg. goo or paper)?

The local dealer has them in stock for $1.50... So, I'll get a new
Yanmar (tm) one.
-- Tom.

Just installed the new gasket. I have had the plate on and off 3
times now; I'm so glad I don't pay myself by the hour... There was a
bit of paint and gunk on the throttle crank itself (the dealers
repainted the engine when they had it). So, I oiled the crank axle
and worked it back and forth a bit. It runs quite smoothly now.
After the first re-assembly the motor showed its old hunting symptoms
to a greater extent than I've ever seen before. However, with the new
gasket in it runs perfectly... Sadly I didn't keep all the other
variables constant. The solar panels have been charging the batteries
and the hour break to run down to the Yanmar dealer probably didn't
let the motor cool off entirely. I'll try it again in the morning.

-- Tom.

[Roger Long]

Tom,

Refresh my memory or check this. Is the hunting only at full RPM? If the
hunting comes back and is not just at full RPM, you might do trials at 100
RPM steps and see if there is a pattern.

--
Roger Long

[t***@gmail.com]

Post by Roger Long
Refresh my memory or check this. Is the hunting only at full RPM?

Typically when it is acting up it can hold ~1000 pretty steady even
with a load but looses power above that if any load is applied and
starts hunting. The cycle always starts with a loss of rpm and may
drop all the way off to slow idle and then a slow recovery. As things
warm up the dips become smaller and smaller. I know what it sounds
like but... I am thinking of taking Wayne's suggestion of getting a
bit of 1/4" clear hose and putting it between the filter and the
injection pump just to confirm my strong belief that the system is air
tight. And at some point I suppose I will drop $25 on the diesel
group. Working the throttle back and forth and lubing the axle did
free things up noticeably. It will be interesting to see if it is
better in the morning.

Cheers,

-- Tom.

[Jere Lull]

Post by t***@gmail.com

Post by Roger Long
Refresh my memory or check this. Is the hunting only at full RPM?

Typically when it is acting up it can hold ~1000 pretty steady even
with a load but looses power above that if any load is applied and
starts hunting. The cycle always starts with a loss of rpm and may
drop all the way off to slow idle and then a slow recovery. As things
warm up the dips become smaller and smaller. I know what it sounds
like but...

With this restatement, I'm thinking along the lines of a restriction.
Remember that Roger stopped needing the electronic pump when he
replaced the rubber hoses.

Is it possible that the hose is kinked or has something resting on or
against it that could restrict flow? Is it old enough that the interior
of the hose could be swelling up?

You might be able to swap hoses to see if the problem switches engines.
I'd blow out the lines to clear any foreign material while I was at it.

[t***@gmail.com]

Post by Jere Lull
Is it possible that the hose is kinked or has something resting on or
against it that could restrict flow? Is it old enough that the interior
of the hose could be swelling up? ...

Well, its all still fairly new, but I'll go over it again. There
certainly aren't any obvious kinks and the hoses look like new from
outside. The total length of hose from tank to injection pump is less
than 10 feet. I can't see bothering to swap hoses but it wouldn't be
a big deal or a big expense to replace them. Good thoughts. Thanks.

-- Tom.

[Roger Long]

If the hunting is pretty much the same over the power normal band, which is
how I read Tom's description, then I'm actually pursuaded against fuel
restriction. A fuel restriction problem should only show up above a
certain RPM. I still think something is unstable in the governer due to
some part sticking. The fiddling Tom just did may have freed it up,
possibly just temporarily. I would be looking at the spool that transfers
the weight motion to the rest of the mechanism if it were my engine.

If it is a fuel problem, it would probably have to be associated with the
engine mounted mechanical pump since it's output varies with RPM and could
create the problem fairly consistently across the power band.

Tom, you do or should have a spare fuel pump on board. It's a quick swap
and I would put your spare on the engine now and see what happens. If
nothing changes, you can just leave it and put the old one in the spares
marked "Used - Servicable". Even though you have a gravity day tank, the
mechanical pump on the engine could be having an effect on fuel flow.

--
Roger Long

[Larry]

Post by Roger Long
A fuel restriction problem should only show up above a
certain RPM.

Noone has addressed my post about an AIRLEAK on the suction side of the
primary fuel pump.....bubbles will drive it crazy.

[t***@gmail.com]

Post by Larry

Post by Roger Long
A fuel restriction problem should only show up above a
certain RPM.

Noone has addressed my post about an AIRLEAK on the suction side of the
primary fuel pump.....bubbles will drive it crazy.

The tank is gravity feed. The fuel pump was fine when last
disassembled and inspected and the problem pre-dates that, but in any
case it isn't required. I could run the fuel line directly from the
tank to the engine's fuel filter... Would that mean anything?

I got a new and worrying symptom today. Yesterday when I was feeling
around in the inspection port one of the cranks fell away with a
"plink". Of course, I'm very aware that the only way to get in there
properly is to remove the gear case and so I was not thrilled by that
development. However, moving the throttle crank back and forth did
bring the missing crank back up to the injection limiter and I figured
ok, maybe the weights just fell back or something. So, with some
trepidation, I turned the beast on and it worked perfectly. Cool.
Now, I just ran it again after letting it sit for the night and it
worked wonderfully for about 15 minutes. I was able to load up the
alternator with a bunch of stuff hooked to the inverter and some fans
etc and had perfect throttle control and was getting ~100 amps out of
the thing in either fast idle or in gear and pushing against the dock
lines... Smoke free and purring smoothly. Then, it started its
hunting again and when I removed all the loads and let it sit a while
it didn't get any better. Hmmmm... What is going on? It has never,
ever done the hunting thing after it has started running correctly
before.

-- Tom.

[t***@gmail.com]

... Even though you have a gravity day tank, the
mechanical pump on the engine could be having an effect on fuel flow.

Hmmm. I'm sitting here listening to the engine run now. It seems ok
and is putting out ~40 amps. But, I'm thinking you may be onto
something. Could it be that the fuel pump is occasionally jamming
with the diaphragm compressed? It would be odd as I have had the
thing apart and all the bits worked nicely and it didn't seem to have
an effect... Still. Anyway, off to put some more load on the thing.

Cheers,

-- Tom.

[t***@gmail.com]

Post by t***@gmail.com
Anyway, off to put some more load on the thing.

And, it's working fine... It is running with about 80 amps of load on
it right now at about 2100 rpm and looks, smells and sounds sweet...
Not, that I'm ungrateful for that, but I sure am confused...

-- Tom.

[Roger Long]

If it continues to run right, I'll be ready to pronounce that the tweaking
and exercising of the governer parts worked out what little left over
manufacturing burr or flake of rust had gotten in and jammed something.

[t***@gmail.com]

Post by Roger Long
If it continues to run right, I'll be ready to pronounce that the tweaking
and exercising of the governer parts worked out what little left over
manufacturing burr or flake of rust had gotten in and jammed something.

Thanks. I keep hoping it will cure itself. I'm not convinced it has
done that though as the order of events goes:

Fiddled -> tested ok
left to sit overnight -> tested ok for a bit and then failed still
hunting when shut down
left to sit a bit -> tested ok did not hunt on start-up...

I'm stumped. And I've kind of given up on the injection limiter per
se. I'm not convinced yet that it isn't some intermittent failure of
the governor but it is a puzzle...

-- Tom.

[Roger Long]

If something in the governer is right on the edge of sticking, it could be
temperature related as the heat reaches those parts. Keep an eye on that
aspect of the puzzle.

--
Roger Long

[t***@gmail.com]

Post by Roger Long
Tom,
The engine that burns more fuel is the one with the control problem, right?

No, the problem engine is using less fuel for the same nominal rpm.

Post by Roger Long
...Turning the adjustment could
cause even more problems if so.

Yes, there must be a reason they don't want users to mess with it.
That could be it.

Post by Roger Long
Get an opinion from someone who actually knows but I'll bet a six pack they
are going to tell you they need to pull the rear case cover and look at that
spring.

I'd happily pay for an opinion from "someone who actually knows", but
simply asking (and paying) the local Yanmar dealers and recommended
independents obviously isn't a good way to get that opinion...

-- Tom.