I have a friend who bought a used 2004 22' Crest pontoon with a 04 Mercury 90 horse 2-stroke. The prop that was on it when he bought it was pretty badly beat up, so he bought a new one. I was appalled by the lack of performance when I first went aboard...at full throttle the tach said we were turning 4800 rpm, but we were barely hitting 12 mph. I'm guessing that the dealer he bought the prop from sold him whatever he happened to have, and suspect that the diameter may be too small for the thrust needed on a pontoon. I don't recall exactly, but I believe he has a 12x15 now. I'm thinking he needs a little more diameter, and a little less pitch. Opinions?