My Tracker 175 and a 50 merc got 30mph fully loaded with a partner and 32 light with a 4 blade 13 pitch trophy prop. There isnt much you can do with those little motors without tearing into them adding more compression with cut heads, porting and larger carbs. By that time you could have traded engines and maintained reliability and longevity. There is a splash baffle you can remove from the cowl to get more air in, but to actually get some real gain, you need to rejet the carbs to give more fuel to produce the addition power, and even then you might get 1-2mph? Enjoy your reliable engine, even though it may be a bit slow or step up to a 50 or 60 horse.