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Yanmar super vibration

12448 Views 47 Replies 14 Participants Last post by  meanderboy
MY YANMAR 3YM30 IS SHAKING ITSELF TO BITS. It is 9 years old and 3000 hours and has run perfectly until 30 hours ago. The engine runs perfectly in neutral to full RPM. It also runs smoothly in reverse at all speeds. In forward gear, it runs ok until I shift into neutral and try to shift back into forward.

Then the engine starts to shake at 1000rpm and shakes horribly and starts a clacking / grinding noise at anything over 1200 rpm. It is truly frightening

On the advice of the Singapore dealer, I replaced the engine mounts and vibration damper. No improvement at all.

Finding an available mechanic here is very difficult, so any suggestions what to look into would be most appreciated.
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Have you checked the valves? If diesels miss, they produce some disturbing noises. If one valve is hanging or needs adjustment, it could produce this condition under load. You are absolutely right to avoid an expensive fishing expedition! Take it piece by by piece to eliminate everything until you are certain what the problem is. Compression test? Maybe try releasing compression when this occurs. If slowly releasing compression on one cylinder has no effect, it might narrow the problem down to either a bad injector or a leaky valve. Have you checked for obvious air leaks in the fuel lines? Maybe give all the connections a tweak, especially those injector banjo fittings which tighten down on the copper washers (use a torque wrench). Do you have a shop manual?
Those super soft , nothing but rubber connecting the engine to the boat, Yanmar mounts are dangerous. A boat was sunk off Queensland last year, when the engine came loose and punched a hole in the hull. Perko makes harder mounts with metal holding things together, if the rubber gives out.
Don't want to throw this thread off the tracks but you are right about the danger of the rubber mounts. That said, to avoid the "flying large projectile" problem inherent in these mounts, cable or Amsteel should be threaded through the upper and lower components so the engine can't go far. It's a good use for four soft shackles.
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