I have a 75 HP Mercury 2 stroke running an aluminum 13 1/4" X 17" prop. I need a new propeller and would like to go to a slightly lower pitch as I'm just barely touching the low end of the rpm I should be at at WOT. I get about 4600 rpm when WOT should be 4700-5200. The problem is when looking at props, they don't have multiple pitch sizes in a given diameter size, at least not in the 13 1/4" diameter that I currently have. The next "lowest" prop looks to be a 13 3/4" diameter with a 15" pitch. Supposedly each change of 1" in pitch results in a 200 rpm change. What about changes in diameter? I have enough clearance under my cavitation plate for the 13 3/4" diameter but I'm not sure about changes in turbulence with the bigger diameter and how changes in diameter effect WOT rpm. Also I have a strong pull to starboard on my outboard, even with my trim tab set at a good 20 degrees to push the outboard over the other way. I use the boat mainly for cruising (21 foot Larivee pilothouse) what's a good aluminum prop to get? Thanks for any info.
-Mark
-Mark