the rule of thumb for the 3 or 4 blade props is this, 3 blade -- run same pitch as the 2 blade ur using but just 1 inch shorter diameter. 4 blade --- 1 inch shorter diameter but 2 to 3 degrees less pitch on blades.


91 surpass; 2 blade == 12/12,13/6,13/8,14/6,14/8
3 blades == 12/6,12/8,13/6,13/8
4 blades == 11/8,11/10,11/12,12/8,12/10,13/4,13,6

these are just general prop sizes,you need to try a few and see what ones work best for you plane.

Good luck,Art