Yanmar 3GM30 Drive Noise/Vibration

[RLaird]

So I replaced the original seized engine with a used, but free wheeling replacement. I kept the motor mount nuts threaded to the original locations and the shaft coupling faces seemed to be parallel and aligned nicely on assembly.
I haven't put many hours (2-3) on the boat since launching for my maiden voyage as the new owner. I noticed some excessive noise and vibration. Not severe, but excessive. Finally I worked my way to the prop shaft and felt the vibration which is emanating from the engine (seems like a normal pulse for the 3GM). I found that if I put some upward pressure on the prop shaft the noise is greatly reduced. Granted, my hand is damping the system but it seems to be also removing some 'contact' pressure on the cutlass perhaps.
There is no excessive leaking of the cutlass. It drips as expected when the shaft is turning to drive the boat.
Would it be reasonable to raise the the two aft engine mounts a few turns each (gradually and evenly) to see if this eliminates the noise and transmission of the vibration???
She will be hauled shortly for the season but I am hoping to check this off the list before next season!
thanks for your time,
Rob
The Legacy

[roverhi]

Have you checked the alignment with a feeler gauge?? Motor mounts can deteriorate and change alignment. When I pulled my 3GM30F to move the engine further aft, the original Yanmar mounts were toast even though they had few hours on them.

[RLaird]

Thanks for the feedback. I haven't taken any measurements yet.
The mounts 'appeared' to be sound when I replaced the motor. No separation or signs of dry rot but they could have been hiding a problem I suppose.
Best,
Rob

[jkishel]

The drips you refer to are not coming from the cutlass bearing, they are coming from the stuffing box. The cutlass is located further aft on the shaft outside the hull. As mentioned, first step is to properly align the engine using a .003 inch feeler gauge. Engine alignment should be checked every year or so. This will also indicate any problem with the coupler, bent shaft, etc. If all that is OK and the vibration persists, you will need to check the cutlass bearing itself for excessive wear.

[Sailmonkey]

Read up on properly aligning an engine. What you have done is not it....further just raising the aft mounts will put additional strain on the couplings.

https://www.google.com/search?q=mari...&client=safari