I have 20 ft Pontoon with 75 hp Honda four stroke. It currently has 4 blade prop with 13 x 15 pitch. This gets me 5100 RPM and 20 to 21 mph at WOT with 3 people.
The 5100 is only at top of RPM range, however I was afraid to go to lower pitch in fear I might lose some speed.
I was thinking of...