So I finally got on her Sunday and took the 88' Formula SR1 311 up to 5k rpms. I had throttle left and barely any trim. My gps said that I was going 53mph which I believe is off because I was running door to door with another boat and there gps was reading 61mph. I have mirage 23s on there now and figure I need to go up seeing I have throttle left. What should be a good prop to move up to. I had the 25+ on there and that was to much so should I go with a 25, 23+, or a bravo 24.

Did you push it past 5k to see if it hit the limiter?? Also what engines/wot range. Summer heat will knock off a cpl rpms so you might be propped right??

454 420hp each. I had plenty of throttle and trim so I don't think it was the cold air or water that allowed it to turn that easy. Did not push it pass 5k rpm either.

Merc 420's are pretty stout motors, bury the throttles and trim er out. If it still has the original ignitions I don't think there is a rev limiter but I wouldn't worry about the rpm unless it starts getting up around 5400. The 420's have a much better valve trane setup than a 454 mag. You need to see where you are really at before you change anything. That boat should run 65+ trimmed out.