have a 1988 16 foot bayliner with a 55 hp evinrude on it. when im by myself , it will get up on plane and do about 27 mph, but when the gf gets in.. a whole hundred pounds , it will only do 17 adn will not plane out.. it has a 12.25x15 prop on it, would i benifit from going to a 13 pitch and...