3GM30F Compression Release Help

[robertsapp]

In the process of getting acquainted with the Yanmar 3GM30F on the H336 we just bought, I pulled one of the compression release levers. Just can't keep my hands off of things. Anyway, it clicked into the down position, and now I can't budge it. How does one reset a compression release lever on a 3GM? I've tried rolling the engine, actually I started it for a few seconds and then immediately shut it off. Ran fine on two cylinders, but I still can't budge the lever. Is it supposed to just pull back to the upright position, or is there some sort of release I have to push/pull?

 

[kloudie1]

It should click back.. Ya might have to remove tthe valve cover and see what gives. The mechanism comes out with the valve cover.. It should have come back when yu started up..or rolled it over.. Takes about a minute to pull the cover (if you have access) and ya ought to be able to figure it out by comparing to the other two. Good Luck.

 

[Dan Johnson]

Robert...

there is a steel ball and spring behind the lever itself on the bottom side that fits into a detent on the lever. This may have failed and locked your lever down. See if you can slip a feeler gage blade behind the lever on the underneath side, against the side of the valve cover, to force back the ball on the spring, then try to lift the lever.

If that doesn't work, follow Claude's advice and pop the valve cover up an inch or so to see if you can free the lever.

The decompression mechanism is really very simple. The lever rotates a shaft that has a half flat end on the horizontal just above the rocker arm end. Rotating the lever moves the half round into contact with the rocker arm and pushes the valve off its seat just enough to disallow full compression of the cylinder charge by the piston. A verticle pin in the valve cover retains each shaft in place.

 

[robertsapp]

Re: Robert...

Thank you both for your help. I'll be on the boat again this weekend, so I'll see if I can figure out how to open up the top of the engine enclosure so that I can get to the valve cover. On a related note, I found a great online resource site for boat manuals that had the 3GM service manual available as a pdf for free download. I now have an exploded diagram of what I'm dealing with.

 

[Rick]

Re: Robert...

Hey Robert
Sounds like good advice. Do you by chance have the link to the manual. Could sure use on of those at home.

Cheers

 

[robertsapp]

Re: Robert...

Just FYI, after looking at the diagram in the service manual and considering the advice I received above, I positioned myself in front of the engine and gave the lever a mighty yank. It clicked back to the normal position - problem solved! I think the ball detent is probably stiicky.