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Old 23-04-2009, 05:50   #1
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Yanmar 3GM30F motor mounts

My Yanmar engine has over 2000 hours on it. It only vibrates at idle. I suspect that one motor mount might be defective. Is there any way to tell if a motor mount needs to be replaced while the engine sets on the mounts?

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Old 23-04-2009, 07:16   #2
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Yanmar says that motor mounts should be changed every two years. That may be but not always in my experiance. There should be a gap between the two metal plates that make up the motor mount. You should be able to just fit a pencil in that gap. If the mount has collapsed and the two metal plates rest on each other, it's time. Also these motor mounts do not like diesel fuel. Whenever you change the fuel filter on the engine I always drape an absorbent rag over the mounts to prevent fuel from dripping on the mount.
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Old 23-04-2009, 08:18   #3
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check you idle speed, It may have slipped and be to low causing the excess vibration.
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Old 24-04-2009, 18:55   #4
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after a few years, yanmar mounts can be adjusted using the threaded rod. the adjustment of the roads takes up the slack created when the compressible rubber gets smashed down by repeat engine vibrations. when you can't adjust the threaded rods any more , it's time to replace the mounts. i got 8 years out of my 2GM20f engine mounts,(500 hrs on the engine) . at that age they were ' 'bottomed out and not adjustable using the threads any more, then there was quite a noticeable increase in engine noise and vibration. if oil dripped on the mount directly under the oil filter you could have one bad mount as the oil degrades the rubber..but at those ages it may be time to replace them all. not a bad job, just a pain. mounts for front (beltside) are different stiffness than for mounts at rear (gearbox side) so buy the right ones and keep them straight while you install them.

fair winds to you.
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