Diameter depends on pitch somewhat. I have three props on my 115hp, a 4 blade AL 15 pitch, a 3 blade SS 19 pitch, and a 3 blade AL 17 pitch. all three are different diameters with the 4 blade being the smallest.
I have a 12.5x17p and a 13.25x16 pitch. Can't reach optimal rpm with the 16p, so that's why I'm asking. Just curious if anyone else is using a 12.5in prop.
