wrote:

Wayne the vibration of that single cyl. diesel had to be obnoxious,
even when it was running good.
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I guarantee it was so bad on a Yanmar YAM-12, (a one lunger)
installed in a 30ft sloop that it broke at least 3 sets of of engine
mounting bolts.

Solution was to install an AquaDrive CV joint. Solved the problem
and reduced the vibration sound level by at least 25dB.

Lew