i just picked up a 24 ft. searay weekender,1980 with a chev. 350 260 h.p. mercruiser.it has a 15x17 prop on it.i get about 26 mph and 3200 rpm.just barely gets on plane.would anyone know if this is the rite prop.i know there are many variables,but i need a starting point.it has trim tabs also.i...