[hamiam]

I am the previous owner of a C&C 30 with a 2GM20 Yanmar engine. I actually does matter; some transmissions are not meant to free wheel. This was the case with my Yanmar. Actually, I believe that they suggested that you put the engine in reverse to lock the shaft. If you don''t have you manual, call a Yanmar dealer. A locked shaft is good both for your engine and for your performance under sail.

 

[hamiam]

A freewheeling prop creates more drag that a locked shaft; leave it in gear while you are sailing!

 

[hamiam]

Depends on the prop. A folding prop will offer less resistance when the shaft is locked. No question about that.

 

[hamiam]

As for the fan analogy; aeordynamics and hydrodynamics, while similar, are two very different mediums. I will try to find the article, however, a free wheeling prop does not necessarily offer less resistance than a locked shaft.