[Navatech]

I get vibration starting around 2000 rpm. Standing above the struts. Engines were replace 4 years ago and now have 300 hours, [454s].
Surveyor suggested alignment. Cost to do it about $1000.00.
My mechanic suggested having shafts taken out to be checked along with the props. About 2100 hours on gear behind transmission.
I'm hauling boat out to have all sea cocks replaced, they are frozen open. I count 8 of them.
Any thoughts on the vibrations.
Previous owner never felt the vibration from the helm.

Vibration can come from unbalanced props, bent shafts, worn out cutlass bearing(s), misalignment and/or from an engine that isn’t firing equally on all holes.

Replacing engines necessarily entails realignment. And that realignment should be double checked about 50 hours afterwards. A step often dispensed with by my (less scrupulous) colleagues. Not a good thing as repowering usually means, at least, 2 weeks on the hard. Boats that have been out of the water get “bent”. A few weeks in the water “straightens” them. At which point an adjustment of the alignment may be required.

You’re hauling out for the seacocks (a wise decision). I’m going to assume you’re going to redo the bottom paint too. I would also send the props for balancing. When they’re off the condition of the cutlass bearings can be inspected. The shafts can also be inspected for straightness. If you’re pulling the shafts consider putting in dripless shaft seals.

Before you pull her get your mechanic to ascertain that all holes are firing roughly equally. On a gas engine you can do that by pulling the plug wires one by one and noting the RPM drop. An electronic tachometer comes in handy. On a straight diesel you can achieve the same result by cracking the fuel line at the injector. A few drops of fuel will leak. On an electronically controlled diesel you’ll pull the injector wires one by one.


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