Vibration at low rpm

[Jimboyyy]

Was able to dive on the boat this weekend and removed much of the past years growth on the bottom. The cutless bearing shows no slack and the prop is in good shape. The only thing I can think that might be causing the vibrations would be shaft alignment. How do I check shaft alignment?

I have also noticed this 1GM likes to be warmed up prior to departure and the vibration seems to disappear under higher rpm.

 

[garyc]

shake rattle & roll is the nature of the beast. It's one cylinder that why.

 

[Papa Bruce]

I have a 2 cylinder that does the same thing. Any thoughts?

 

[Paul F]

Found that a three blade prop makes a huge difference in smoothing out the drive train.

 

[Jeff]

I have a 3 cyclinder that doesn't like certain RPM ranges. I stay above or below those.

 

[Jimboyyy]

Thanks guys!!

 

[fifedog]

Jim - I like to mumble Capt Quint's "Spanish ladies" (Jaws) during the low rpms.
Also, my diesel mechanic says that warming those Yanmars in neutral does nothing for the engine. Running them in gear for 10-15 minutes keeps them happy.