I have a 1988 Mariner 100 hp outboard and am pushing a 24' pontoon boat with a top deck on it. If I try to accelerate quickly the motor will rev very high but the boat will not speed up, as if the prop is cavitating (?). I can only accelerate slowly to get to top speed. I have no idea what prop pitch I have, as the boat and motor were bought used, separately. I suspect the prop does not have enough bite to push all the weight, and the pitch may be wrong. How can I tell what the proper pitch / propellor should be? I do not have a tachometer so I do not know what the rpm's are. Any suggestions would be greatly appreciated. Thank you!