I'm running a 1973 850 85hp mercury on a 16' trihull bass boat with a dry weight of 850 lbs, hitting 35.6 mph (GPS) @ 5000 rpm at WOT. I bought the 13 3/8 X 19, SS Ballistic, for $50.00 bucks. Is it the extra 3/8 inch holding the rpms back, or can I send the prop to a prop shop to change it to...