Prop size and factory spec.

You mention "occasional, long distance trips at low -legal- speeds".

How often (roughly speaking) would 'occasional' be in this context?

Do you primarily operate in areas where there are no speed or wake restrictions, and you can go happily 'on the plane'?

 

You might get some advantage out of a five-bladed prop if running at those speeds, but it wouldn't amount to much.

 

In all honesty some 80% of my boating is in speed restricted areas. Biggest advantage of higher speeds is the increased daytrip range.

 

With apologies to Peter Benchley... You're gonna need a bigger boat.. Or at lest a longer one... If you spend most of your time cruising at 10 knots you're in a very inefficient range.. Either slow down some or get a longer boat so that you're not pushing hump speed. You actually are making more wake than if you were planing and you're in a really inefficient operating point. You're burning a lot more fuel per mile than if you had a longer hull that was closer to hull speed.