I have a 1978 Chrysler 45hp kn a 1979 Chrysler 15' sport satellite. It runs great, but doesnt plane st all. It has I believe a 10.375 x 12.5 prop. With my wife and I on it we do about 19mph. Any more than that and we do like 12mph. I was thinking of going to an 11 pitch. Would a 10 pitch be too...