Hard to say. What is the horsepower of your engine and what is the factory recommended WOT RPM for your engine? It's nice to go fast, but it's more important that you don't destroy your engine by overloading it.
You want to match your prop to whatever is recommended. For efficient performance, it's critical that your engine operates within the RPM range recommended by the manufacturer. Matching the right prop for the load is the most significant factor of RPM adjustment.
Generally speaking, a pitch change can increase or decrease your RPM's and bring RPM's into the recommended range. A 2" increase in pitch (for example, from 17" to 19") typically results in a decrease of approximately 300-400 RPM.
You should be looking for a 15 tooth spline, thru-hub exhaust prop and your prop diameter can vary from 14 1/4 to 15 1/4".
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1987 V20 w/1987 150HP Yamaha on a Shoreland'r Trailer
1978 16.5 Airslot w/1996 120HP Force on a Four Winns trailer
1996 V21 w/1993 200HP Mercury on a Shoreline Trailer
All towed by a 5.7L Hemi Durango.
If God didn't have a purpose for us we wouldn't be here, so
Live simply, Love generously, Care deeply, Speak kindly.
(Leave the rest to God)
Silence, in the face of evil, is itself evil. Not to speak is to speak, not to act is to act. God will not hold us guiltless.