I installed a 1999 50hp johnson on my lund 1650 explorer. It has a 12.5x13 pitch propeller now. (The motor came off a pontoon). At WOT I'm running about 5800-6000rpms. I only ran it that have for about 20 seconds cause I think this motor is supposed to be max 5500rpms. Right now it tops out at 25mph. Total weight with people is about 1350lbs. from a little research I though I may need a 12.25x15 pitch. Is this correct?

im surprised to see only 25mph with this 50hp. This boat used to have a 25hp motor and I got exactly 20mph out of it.