hi i have a 1974 baja 16 foot speed boat with a 1974 johnson 115 hp outboard. i was wondering if i could get more speed. now i get about 45 on the boats speedometer (im not sure that it works good) but the guy i bought it from said he got 56. does that seem right? anyway how can i get more top speed? i now run 5500 rpm with the cavitation plate about even with the bottem of the boat . i do have power trim. also what is a hydrofoil for an outboard, how much do they cost and what do they do? thanks!