I learned to foot behind a 15 ft. runabout with a 85HP Mercury OB and 40 MPH was the top end. Since then, I've foot behind my 79 S&S, my 87 Prostar 190, and my 95 Maristar 200VRS. I've never tipped the scales more than 185 lbs and I've never had to run any of the inboards WOT to keep it at 40-41 MPH. If you glide across the water (and not plow), extra passengers in the boat will affect the top end speed more than the footer, even on one foot. The powerslot and a 4 blade prop will give you more hole shot for deep water starts if you have a few people in the boat too.