working on my yanmar 2gm

[tradecode]

hello, this is the engine in my s2 9.2 1982 that i just purchased..

the engine tach only shows it revving up to about 2k rpm's, i read that this thing should do 3,500 rpm.

i read that the mixing elbow either needs cleaning out or replacement, so i thought i would try that.

there are two levers on top of the engine that i have no idea what they are, but they seem to work best when pushed all the way to the forward(towards the alternator and belts.

below the throttle is a lever that seems to shutoff the engine, i am not sure what that is.

any help is appreciated,

edward.

 

[Davidasailor26]

Someone with a 2GM might be able to confirm, but the two levers on top of the engine look like they might be decompression levers. If so the engine will definitely run better with them in the operating position. The lever below the speed control lever is the engine shutoff lever, so it makes sense that it stops the engine.

The engine manual probably has more insight - http://j30.us/files/yanmar-manual.pdf

Before you dig into the RPM issues too much check the speed with an optical tach. You can get one cheap at Harbor Freight. The tach on the panel is sometimes inaccurate. Also, is the speed you measured in neutral, in gear at the dock, or in gear underway? And was there any smoke at the time?

 

[Richard19068]

+1 on everything Davidsailor26 said

See the attached page from the manual

 

[tradecode]

the speed i measured, using the tach in the control panel, was performed in neutral at the dock.

i will go to harbor freight to purchase an optical tach.

thank you for the manual, i will get that printed and bound at office depot.

thank you.

following is a link to an audio of the engine running.

https://files.catbox.moe/kk6qd5.mp3

 

[Tally Ho]

Someone with a 2GM might be able to confirm, but the two levers on top of the engine look like they might be decompression levers. If so the engine will definitely run better with them in the operating position. The lever below the speed control lever is the engine shutoff lever, so it makes sense that it stops the engine.

The engine manual probably has more insight - http://j30.us/files/yanmar-manual.pdf

Before you dig into the RPM issues too much check the speed with an optical tach. You can get one cheap at Harbor Freight. The tach on the panel is sometimes inaccurate. Also, is the speed you measured in neutral, in gear at the dock, or in gear underway? And was there any smoke at the time?

Yes, those are the decompression levers. 1 for each cylinder. They should be “closed” normally so the engine builds compression.

The lever below the throttle is the fuel cut-off that starves the engine of fuel to shut it down.

Once she starts, she doesn’t sound too bad..

Does it start easier after it is warmed up! Mine takes a little longer to fire up when I start it the first time in a week or longer…it is also impacted by ambient temperature.

When you were trying to up the rev’s, did you have the throttle lever pushed to the max? The throttle cable is adjustable, and maybe it is loose or not adjusted right, so you are not giving the engine WOT. You could try using the on-engine lever and see if you can get WOT there.

Your fuel-cut off plunger (or whatever your S2 uses) should be pushed down to start and run the engine. Verify that the cable for that is also fully opening the fuel flow when the plunger is down.

Yes, your Tachometer could be off. It sounded like you got the revs up some in your recording, but you didn’t let it stay revved up very long.

Mixing elbow could be plugged up and need replacing. But let’s rule out the easy stuff first.

As reference, here is my 2Gm20F running... in neutral at the dock, at a fast idle.

Greg

 

[Dalliance]

I have the same 2GM engine in my ‘82 H30. Tally Ho has already covered everything that I would have mentioned and more, so no need to repeat. You’ve come to the right place.

 

[Scott T-Bird]

I don't see a cable attached to your shut off lever. The cable is normally attached to a handle mounted in your cockpit that you pull when you need to shut the engine off. It's not clear to me what you do. Do you have to reach inside the engine compartment and push that lever by hand?

Assuming that your tach isn't too far off (and by all means, test with an optical device), the low rpm's is very concerning. It is often associated with low compression. You can do a simple test for blow-by by removing the oil dip stick while the engine is running. If there are significant puffs of air blowing out the tube, you have blow-back. I'm no mechanic but I believe that will indicate that piston rings or piston walls are damaged and compression is low. These are significant issues possibly requiring engine re-build.

Some blow by is normal, if you should detect just insignificant puffs.

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Compression loss can be caused by being over-propped for a long time. These are circumstances I have experienced with an old diesel engine on my first sailboat.

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Also, seeing that there may be something funky about the shut off lever not being connected, check the governor link on the throttle control. Perhaps when you think you are at full fuel delivery, maybe you are not!

 

[Tally Ho]

The rope on the throttle linkage may be a clue….

Greg

 

[Don S/V ILLusion]

i had a diver in the water today inspecting my prop.. he tells me that it is very corroded, and needs replacing.. he did not bring his tools to actually pull the prop so that i could take measurements... :sigh:

does anyone know what the prop specs/measurements are for this 1982 s2 9.2 are? shaft size, etc?

thank you.

The prop is sized to an engine generally, not the boat. What engine?
Your post takes us off the topic, a maneuver not proper.
Why not post your question as a stand-alone topic for everyone to see and include the engine/transmission model?