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  Topic Review (Newest First)
10-02-2009 06:49 PM
roline Idle on the 2GM20 should be around 800 RPM. Lower and it vibrates, shakes and sounds like the pistons are ready to launch. I don't like to have it much higher believing it is hard on the transmission when shifting in, out of gear. There is an idle adjustment screw that you can use to adjust the idle to make it independent on cable stretch.
07-07-2008 03:52 PM
gsyversen if it drops one cause of air that would be permanent though right, mine works just fine during normal use, its just switching from forward/reverse to neutral and just for I'd say a second...

What's wrong putting in a great suggestion to an old original post, I try to search archive before posting and this was exactly on my topic so why start a new thread....
07-06-2008 10:17 PM
Originally Posted by fullkeel7 View Post
Note to self with palm of right hand to center of forhead: SMACK! Before typing a 5 min. reply, check the date of the original post! SMACK! SMACK! How many times do I have to do this before I learn....SMACK! OUCH!! Da..!
It's funny, the old timers tell the folks who are new to sailnet "Have you tried a search on this topic? It's been discussed a million times." Nobody tells them to also check the date....

Old thread, but good info. If my diesel starts acting up as stated I'll remember some of what I read here.


BTW I had a yanmar 2QM20 I thought they ALWAYS vibrated like that.
07-05-2008 02:05 PM
fullkeel7 Note to self with palm of right hand to center of forhead: SMACK! Before typing a 5 min. reply, check the date of the original post! SMACK! SMACK! How many times do I have to do this before I learn....SMACK! OUCH!! Da..!
07-05-2008 10:08 AM
ericroline 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.
07-02-2008 12:13 AM
gsyversen 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....
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.


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.
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.


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
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