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Petar 12-15-2005 08:22 PM

Yanmar 2GM20F

My Yanmar 2 cylinder diesel with 800 hours on it is vibrating excessively (1/2 - 3/4 inch on each side) on minimum rpm in neutral or engaged even when it is warm. Once I raise the rpm just alittle (say 200 rpm) vibration stops and it runs nicely without vibrationat all. Engine foundation have very good rubber cushioning on each anchor point.

Any suggestions whay is this happening?


tahitisail 12-16-2005 07:01 AM

Yanmar 2GM20F
I have a 300td mercedes and that has five cylinders and you would think it is going to jump out of the car at an idle but when at higher rpm it settles down to what you would expect. I''m not sure that my 2gm20 idles as rough as your engine but it only has two cylinders and I expect it to be rougher than a 5 cylinder engine. Like your engine, when at a higher rpm my yanmar settles down to a "quiet" roar.
I think it is interesting that the electronically controlled diesel engines are so quiet,say a 5 cylinder dodge sprinter engine, but that''s new technology for you and we sure don''t want any new electronics in our sailboat engines that we might have to work on out on the pond.

Techman 12-17-2005 04:23 PM

Yanmar 2GM20F

I suspect the shaking while idleing problem is due to bad motor mounts. I used to have a 300D that did the same thing and replacing the motor mounts stopped the problem.


firemanbob 12-19-2005 11:36 AM

Yanmar 2GM20F
Had the same thing with my yanmar. never gave me a problem but spent little time at idle. I had good mtr.mounts.

bubb2 12-19-2005 05:03 PM

Yanmar 2GM20F
I have the same Yanmar in my Beneteau. I put about 50 hrs on the engine per season. The engine has about 300 hrs total on her as I write this post. During the third season the engine started to vibrate at idle so bad it would shake the whole rig. Sounded something awful. After she gained some rpm’s she would smooth out. This puzzled me for some time. What I found was that my throttle cable had stretched and had dropped the idle speed down. Causing the engine to drop a cylinder (firing on only one.) After readjusting the cable (on the left side on the engine as you are facing it) to bring the idle speed back up, no more shaking. Let me know if it works for you, Regards Mike

Petar 12-24-2005 03:26 PM

Yanmar 2GM20F

Thanks fot the hint. I will certainly check it out. I talked to some engineers who said that the problem might be the dirty fuel nozzles. I have checked all four engine mounts and all seem to be in perfect condition.



Neicy 12-27-2005 11:48 AM

Yanmar 2GM20F
I believe you and I have the same boat, a Dufour 31. I cannot remember your year, but it was close to my 77. Mine still has the original Volvo. I also have the vibration you describe. I am not sure if it is as bad. The reason I am so aware of the vibration is it makes the fold down table in the salon area rattle like crazy until the boat is in either forward or reverse. I was told it was because the cutlass bearing were worn and work was needed. Within the next week the boat is being hauled out and this is one of the items on the list. I will let you know if it makes a difference.

Petar 01-03-2006 07:27 PM

Yanmar 2GM20F
Hi Denise,

My Dufour 31 is built in 1979. I have hauled out my boat in March when I was purchasing it in Seattle. All seemed OK with no clearances apparent. In any case (with my limited engineering knowledge) I do not think there should be any vibration due to lose shaft / worn out bearings when the engine is in neutral and shaft not turning. I spent my holidays working on interior,renewing cushions and building that instrument housing to relocate my nav instruments so had no time to look into engine. I plan on hauling the boat sometime in March when I will look into this one as well.



gsyversen 07-02-2008 12:13 AM

got referred to this thread on my post about similar vibration, did you ever figure out what was causing this ? also how do you check the idle speed my manual wasn't clear enough for me :)

hope this someone's still reading this thread....

ericroline 07-05-2008 10:08 AM

The 2GM has decompression levers that you can engage at idle to see if you have a dead cylinder, If you do, lifting on level will have no effect, the other will kill the engine.
Lost cylinder at idle could be air in system at that injector, bad injector or low compression in that cyl.

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