[Bushwacker]

My 90 HP "115" would turn a 13 3/4" diameter x 15" pitch SST prop to about 5600 with light load and 5300-5400 with heavy load and top raised. Was able to raise motor 1" and picked up about 3 mph relative to aluminum prop of same size. Your motor should be stronger than that so might be able to handle a little more pitch or diameter, but I'd start with that, and stay with aluminum or composite till you get it dialed in for the load you normally run. Better to over rev than under rev!