Engine vibration when prop spins in neutral while sailing

[SV Pretty Lady]

I don't know if this is normal, I am new to this so please forgive my ignorance. Took boat out yesterday to sail. Had the stairs off to cool the engine (other problem that was solved) and during sailing, I noticed the engine shaking quite a bit when the prop was left in neutral to spin freely. Not a small shimmy, but enough to get sound to get noticed, and upon inspection, motor was shaking quite a bit all over the place.

This must be an issue because the new PYI dripless seal that was put on leaks .... a lot!!! I noticed this back at the dock. I spent a lot of money to get that leak fixed with this new seal and the new one leaks worse than the old one. It was burped by the workers when returned to me, so I assumed all was well.

Engine shaking....motor mounts fatigued? Which could cause vibration and possibly make the shaft seal leak? I am sure this might have been discussed in a previous post, but I can't seem to find it right now. Any help much appreciated.

1988 Catalina 34 with M25 Universal

[Jon W]

Did you check that the hold down hardware for the motor mounts are tight?

[Ron Hill]

SV P : BTW, you should have an M25XP if it is the original engine.
Did you go down and look at the spinning shaft between the packing gland and the transmission.  Wondering if the connection is correct when they "worked" on the PYI.

A thought

[Ed Shankle]

Was the engine running at the time? If so, low rpms will cause the engine shaking. If the engine wasn't running, you should have the transmission in reverse to prevent the prop from spinning.

Regards,
Ed

[Bill Asbury]

Sails up, engine off, gearshift in reverse is my routine...

[mainesail]

A bad alignment or mounts can do this.... The prop should spin easily and be vibration free when in neutral. Any noise should be very quiet as in barely perceivable.

[Jim Hardesty]

Could be anything in the drive train.  My guess would be the cutlass bearing.  With the engine running the vibration wouldn't be noticeable, with the engine off notice it.
  What do you have for a prop? 


Jim

[SV Pretty Lady]

3 blade non-fold prop. Raised the motor mounts band that made a big difference with vibration under motor. Haven't tested under sail yet.