So.... I currently run a 15P prop. I am at 5200 RPM. Should I go to a 13P or 11P. If I understand the whole prop thing you gain about 200 to 300 RPM per 1 inch of prop change. I appriciate the help.
Since you are only able to obtain a RPM somewhat lower than the maximum rating given by your engine manufacturer, you would need to decrease pitch. Decreasing pitch would increase your RPM. For every 1" of pitch size, the effect will be approximately 200 RPM in theory.
Best thing to do is to mess with how the motor is set-up on your boat before buying another prop. Try raising the motor on the transom 1 or 2 holes and see how it behaves.
I have to buy a new prop since my son hit a rock so, I am trying to maximize my money. I have tried messing with the motor height and think that it is at the best possible setting.