2GM20, very bad vibration

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A

Alain Viua

I have a 2GM20 Yanmar in a Hunter 28.5. I'm getting a bad vibration on acceleration once the engine warms up. It doesn't vibrate in neutral or reverse at 2500 RPM ! It doesn't vibrate to when the motor is cold. Only motor warm and in foreward, beginning at 1500 RPM This thing is vibrating very badly. Please Help.
 
Jun 3, 2004
123
- - Deale, Md
Bad vibes

Here a few things to check (working from the engine to aft), if you haven't already done so: Loose engine bedding nuts; cracked or broken engine bed frames; loose or misaligned engine/shaft coupler; failed or failing packing gland; shaft out of alignment; bent strut; worn out cutlass bearing; bent or misaligned prop. If all is well with these external engine parts, I suppose the problem could be something amiss within the engine and for that you may need a Yanmar expert. Good luck and keep us posted on how things resolve.
 
Dec 3, 2003
2,101
Hunter Legend 37 Portsmouth, RI
Warren, you didn't mention...

...fouled prop (barnacles, etc) or something wrapped around the prop (rope, debris, etc). A lobster pot warp got me earlier this year.
 
Jun 2, 2004
27
Hunter 27_75-84 Red Bank, NJ
Go for a swim

Before you get yourself wraped around the prop. have a look. Had the same problem cleaned the prop and all was well.
 
A

Alain Viua

No No

I chekc the prop and it is OK. In reverse way, no vibrations
 
C

Clark Chambers

More than one cause

I had a very similiar problem and it took awhile and a number of fixes to solve the problem. The engine was out of alignment and the strut bearing was worn out. After fixing both, I still had the same problem. As a last resort, I added fuel conditioner. After about 4 times out, running the engine about 1/2 hour each time, the vibration went away. Trouble sometimes runs in pairs.
 
Jun 3, 2004
347
Hunter 30_74-83 Lake Lanier, GA
Alain,

I understand your problem to be a vibration at 1500 rpm when the engine is warm and in foreward gear. The vibration is not occuring under other conditions. If this is correct. You need to change the oil in the transmission first. If this action does not resolve the problem, Then the trans will need to be disassembled and inspected for slipage of the drive cone and foreward gear. I'm currently repairing a similar transmission with the same symptoms. Pat McCartin Inland Marine Diesel Buford, GA imd_ga@hotmail.com
 
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