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any help would be appreciated.

my 2gm is an original from 1982.
it has been running fine and I am the original owner
the filters have been changed regularly

this season when launched it started normally and ran for ~5minutes before violent shaking and stopping!

now it will not start at 1/4 throttle( were it always did) I can start it at 1/2 - 3/4 throttle it starts and runs smoothly when I let it warm up and try to throttle back to neutral it starts to shake violently and stop.

I have bled the system to no avail. It was suggested to try starting on one cylinder at a time to see if they are equal and they are.

any suggestions at what I can look at or what may be the problem


thanks
 

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you can loosen one high pressure line at a time when the engine is running at the speed where it is not shaking. this is like shorting a spark plug on a gas engine to see which cylinder is not firing. if that makes no difference in operation , that is the one not firing. be careful because the high pressure fuel can give you blood poisoning if it penetrates your skin. i suspect one of the cylinders is not firing.
 

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Maybe your throttle cable has slipped causing it to idle to slow and having to use more throttle than normal to start
 

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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
 

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Rule #1
The last thing you mucked with is the first thing to mess up.
 

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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
I will second that.

Sometimes it's not even necessary to adjust the cable itself. There is a detente where the cable attaches to the throttle assembly that can be adjusted easily by turning one (maybe two?) nuts. Adjust it a bit and the cable will not be able to pull the throttle assembly back as far, and the idle rpm will stay higher. It will only take about 30 seconds to make the adjustment.

P.S. Welcome to SailNet!
 
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