BC,

Cavitation is caused be the Prop not having enough water in Choppy Sea.
Reduction Gearing has nothing to do with it.

You're a Pretty Poor sailer if you are depending on a small Aux, Engine
to replace Sails in a Seaway. Even Trawlers hoist a steadying Sail in a
Seaway to improve ride quality




http://community.webtv.net/tassail/ThomPage