Originally Posted by stevemac00
John, on my 31 with MaxProp it seems I have to take an RPM that causes the least cavitation. That depends on wind direction, waves, etc. but usually around 2200-2400 which yields around 5kt. When I take it up to 3000 or higher the cavitation is terrible and I only get a slight increase in speed. Do you have that issue?
Can't say that we have had any cavitation issues. We don't have a max-prop, though (wish we did!).
With a clean bottom and prop we get about 5.6-5.7 knots at 2700 rpms, and can push it up to 6.0 at 3000 rpms. If the bottom or even just the prop is fouled, there's a big drop off in performance. Ours is a 15" fixed 3-blade. I seem to recall Larry (Asylum) reporting as good or better performance from his fixed 2-bade.
Personally, I would want a cruise rpm that gets the engine up to about 80-85% of the continuous rating. Even at those rpms, we are burning only about 1/3 gph, and of course the alternator is cranking out more amps too.