Hi, I have a 1977 Johnson Stinger 75 hp long shaft model mounted on a 1977 Sylvan Sportster, just curious as to the proper rpms that it should run wide open, I recently installed a tachometer but haven't had time to make it to the lake yet to see what rpms it runs. It currently has a 13.5x15 prop on it, and came with an extra (dinged up) 13.75x15 prop also, both 3 blade aluminum. It usually runs okay, especially if I'm alone or with my girlfriend plus fishing gear, trolling motor, two 6 gallons tanks of gas, etc. but if we ever try to pull a skier or a tube with more than two people in the boat it has a difficult time getting on plane and up to the speed it normally runs wide open.