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.

On Mar 20, 12:10 pm, "Roger Long" wrote:
... 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.

On Thu, 20 Mar 2008 14:01:05 -0700 (PDT), "
wrote:

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)

On Mar 20, 5:55 pm, Bruce in Bangkok wrote:
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?

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.

... you may have clogged filters -
change them all and try again.

It is not a filter problem.

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.

On Mar 20, 5:55 pm, Bruce in Bangkok wrote:
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.

On 2008-03-20 23:55:17 -0400, Bruce in Bangkok said:

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.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI trips & tips: http://homepage.mac.com/jerelull/BVI/

On Thu, 20 Mar 2008 21:44:31 -0700 (PDT), "
wrote:

On Mar 20, 5:55 pm, Bruce in Bangkok wrote:
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.

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.

... you may have clogged filters -
change them all and try again.

It is not a filter problem.

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 :-)

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)

On Mar 20, 9:46 pm, Bruce in Bangkok wrote:
... 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.

On Thu, 20 Mar 2008 22:22:42 -0700 (PDT), "
wrote:

On Mar 20, 5:55 pm, Bruce in Bangkok wrote:
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)

On Fri, 21 Mar 2008 07:25:49 GMT, Jere Lull wrote:

On 2008-03-20 23:55:17 -0400, Bruce in Bangkok said:

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.

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.

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.

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)