"Garland Gray II" wrote in message
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"C. S." wrote in message
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As somebody else pointed out the answer to the "no vibation" may be
counter balance. There is about one meter of free shaft between the
bottom of the boat and the support in front of the prop. Maybe the shaft
flexes enough to counterbalance the missing blade? But why is there no
power in reverse?

C.S.

I can't think that's the answer.
If the shaft flexes from centrifugal force (and I would hope it wouldn't
flex much anyway), it would be pulled toward the single blade rather the
opposite direction which would be necessary to counterbalance.

Now I don't follow. I think the trust from the single blade would push the
shaft to the opposite side and thus generate a counterbalance effect.

That's what probably happens with my saildrive, which can move on the
rubber motor mounts, accentuating the shaking.
I would expect your shaft to be more rigidly secured than my saildrive,
and may not allow this.
I can't explain the difference in thrust.
Under sail, if your engine is in neutral, does the prop open up and spin ?

It does spin but not very fast so I don't know if it is open or closed or
somewhere inbetween.

C.S.