Another prop question: 20' MA advice?

[rkarran]

Hi all. I've had my new-to-me 1979 20-0 Master Angler for just over 3 weeks now and am slowly working the kinks out. I keep adding stuff to the list, unfortunately.

I believe I am overpropped and wonder how to go about the analysis of the issue to correctly prop the boat.
The motor is a 1993 Evinrude 150hp Ocean Pro mounted at correct height on the transom currently turning a 15 x 17 SS cupped 3-bladed prop. Single, maybe double cup.

The Evinrude book says this motor should turn 5000 but I'm only getting 4500-4600 at WOT when trimmed way out, one person, full fuel.

I guess I should record speed at various rpms using this prop as a benchmark? My ultimate goal is an economical cruise speed. I'd like to hope that I could find some other props to try (I'm in the Tampa Bay area) in order to find the right size. Cost is a primary concern to me so i can't spend a lot on experimentation.

I don't want to reinvent the wheel, but rather learn from the experience of you SC guys that have been there - done that.

I have searched the archives but I always find a different variable that doesn't apply to my case. Any advice, suggestions, comments are appreciated!!