correct propeller size

[merrillfrolfin]

I have a 1988 mercury 115 hp 6 cylinder outboard. It is on a 1988 glasstron conroy bowrider. I would like to know what size pitch and diameter propeller I would put on it. I believe the 19 pitch prop I have on it now is running at too high of rpm's around 5700 rpm's at WOT. WOT range for the motor is 4700-5200 rpm's. Any insight would be greatly appreciated.

 

[steelespike]

Re: correct propeller size

My 89 after market service manual indicates 5000-5500 rpm.
While the boat is fairly light at about 750 lbs. I wonder if the tach may be a little optimistic.
Do you know your gear ratio?
Prop calculator indicates with a 2.00 ratio and 12% slip speed would be about 45 at 5700.