On Thu, 24 Feb 2005 20:26:42 -0500, Jeff Morris
wrote:

A prop calculation will cost you an extra 50 cents, but your goal
there should be to have a large enough prop to handle the power, and
the engine reving at a sweet part of its power curve. My rough guess
(and admit this is one area I never really understood) is that the
blade area your prop is small for the horse power you may be putting
through it - this would cause cavitation.

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Propping a sailboat is always a big tradeoff between sailing
efficiency and motoring. For motoring a big 3 or 4 bladed pop is
ideal for a displacement hull but that is deadly to sailing
performance unless you got a feathering prop, and that is another
level of compromise and expense.