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)