Have 15 HP 94 Evinrude short shaft rope start on Tracker JON style 18/48 flat bottom Bass Boat. Use it for fishing in the rocky river. Needs new prop. Old one is 9.5X12.5 which I think was too much pitch. Loaded boat typically weighs 1400 to 1600 lbs. I think max speed possible with perfect prop should be 20 to 24 MPH? Trying to decide between 10 inch pitch Aluminum or 9 inch Stainless? Does anyone know what the Redline RPM for this engine is? We seldon are able to go very fast or run WOT. Any suggestions much appreciated.