My prop is three blade alum. and is beat up badly. Ive looked at the props IBoat has to offer @ around $80. (four pitches 61/2"3blads,71/4" 2blades,8" 3blade, 81/2" 3blad ) Would anyone hazared a guess as to which i should gamble on with a 75lb Kaboat inflatable (about 4.5X16ft flatbottom with...