One of the answers to the fact that a fixed prop is only efficient in a small regime, and thus every prop design is an exercise in compromise, is the variable pitch prop. I've seen them on airplanes, large ships and on sailboats. Not so much on power boats. One would think a planing yacht would be THE place to have one.... But I haven't heard of any..... Anyone know of props in the 20-30-40 inch range that are commercially available and in use? Any brand names?