By the way my pitch is 21" 5300RPM 50MPH WOT. (Maybe 5500 with some wind in the stern)

I'm thinking of a new prop with 20", that might give me +200RPM and better fuel economy. With current prop it sounds like the engine is working hard between 3600-4000, and thats the range where I want it to run smooth.

Any tips/comments ??? ???