Just bought a 2000 Starcraft pontoon a 240 classic. It has a 50 horse mercury on it. Slow speeds is fine but 3:4 throttle the engine Revs up almost like it’s out of water. Could it be a prop issue as in wrong prop? I can’t read the numbers well on their. I can read a138p maybe at the end? Is there a trick to getting the numbers more clear. 24ft toon