a freind of mine has a nice 10' hard bottomed inflateable. the boat has a 25hp motor with a wedge. the motor is mounted as low as it will go, could raise it like 2". he has put this whale tail lookin thin on the lower unit and it has a tiny ass 3 blade prop. also has trim tabs that are like 8" long. right now it will run like 25 and planes out well. I am thinking jack the motor up and play with the props. what kind of top end increase might be available?
One of the local outboard gurus told me to try raising (jacking up) the motor when we were having a Dinghy race one time. I have a 10' hardbottom with a merc 15. The whale tail made a huge difference on mine. I think adjustable trim would help too. Seems to me that the biggest gains are found by removing or re-positioning weight.(My fat ass)