New 90HP ELPTO, was getting 6000 RPM's with the prop I had from my Force 85HP. Pitch is 19. Don't know the Diameter.<br /><br />Just purchased a New Black Max 12 3/4 X 21 to decrease RPMs to recommended 5000-5500 at WOT. Now am getting 5100 RPM (with boat fully loaded, gas, kicker, gear)<br...