Does anyone have experience with replacing the motor mounts for Yanmar 18hp diesel (factory installed)? Having problems since boat was pulled out for bottom painting--shuddering and noise at any speed, engine running rough. After changing oil & filters, put back in water to head back to New Smyrna, then we couldn't accelerate even to 2500 rpm without vibration. Returned to marine where they "bled" the line to get air out it, but problem got worse on the way back. Towed it back to marine, where they said the cutlass bearing had to be replaced and alignment needed to be done to tighten engine. All that was done, but no improvement. NOW, they say we need to replace motor mounts--is this normal for a boat this new with only about 100 hrs/year use? Any suggestions--this is becoming a "money pit" because they just keep throwing repairs at us? Trying to get info from Hunter Marine, but no response to calls yet. Thanks for any help!
2002 Hunter 306 engine mount replacement
- Thread starter dgrunderman
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Your biggest challenge is to determine if the engine is running rough or if you have a mechanical issue. Some air in lines could cause a 'rough' running engine as could dirty fuel or poor air intake. A max of 2500 does indicate a problem - I take it the engine spins up well in neutral? If not, then the issue are with fuel/air/compression. If it does run smoothly in neutral (I know, no-load doesn't tell the whole story); the haulout could have affected the alignment of the prop strut, a propellor blade or bend a shaft. Tough situation but you have to try and isolate it to either the engine or the support mechanicals.
Just a guess, but you may have them check the shaft. I would not be suprised if they bent the shaft when they pulled the boat (it does happen).
Be sure that if it is a motor mount that they install the correct one. They are different fore/aft on the GM engines.
I must assume that everything was okay on the way to the yard!
Be sure that if it is a motor mount that they install the correct one. They are different fore/aft on the GM engines.
I must assume that everything was okay on the way to the yard!
Bent shaft is a big probability.. and now that they have charged you a good bit for stuff that was not wrong, they may be willing to replace the shaft or straighten it to correct the problem.. Start the engine and put it in gear at idle.. watch the output flange on the back of the transmission.. if it is moving the transmission in a small circle and the engine is kinda lolling around, the shaft is the most likely culprit.. and it was probably bent when they picked up the boat with the aft sling on the prop shaft.. If you have a picture of it in the slings, ya might be able to use that for evidence..
A precise way to check is to check the alignment of the shaft (feeler gauge, flange disconnected, shaft supported) and then rotate the prop 180 without rotating the transmission flange.. if the alignment is different, the shaft is bent..
A precise way to check is to check the alignment of the shaft (feeler gauge, flange disconnected, shaft supported) and then rotate the prop 180 without rotating the transmission flange.. if the alignment is different, the shaft is bent..
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I have also read on this site that sometimes the transmission doesn't fully engage causing vibration. Put the transmission in gear forward and then reverse. Test both ways see if the vibration is still there.
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