I just purchased a 2003 Fisher Freedom 220 DLX 22ft with 26 inch pontoons with a 2010 Mercury 115HP Optimax with a 13.5 Diameter 17 pitch SS propeller. The motor was checked out and parts replaced recently before I would buy it. I don't have any past references on how it ran before me. The issue is at WOT my RPMs never get above 4500. If I adjust the trim beyond 4-5 bumps then the motor will lose power and I trim down. Once I shift to neutral I can power back up and she runs fine as long as I trim down a bit. RPMs never spike. At 100% trim down the motor runs perfect but only at 4500 RPMs. Speed is calculated by GPS at 21. I think I need to reduce pitch based on articles and vids I have watched. Any suggestions? Max RPM according to some Mercury manuals I have found suggest 5000-5500/5750???