My boat has a 1987 88 H.P. Johnson motor. While on the lake Sunday, I hit something in the water. The water level was coming up and there was a bit of junk around, so I wasn't going very fast. The boat will move in forward and reverse, so long as I don't go above approx. 10 % throttle. More than that and the rpm's climb but I don't go any faster. The stainless steel prop appears to be OK. All thoughts and suggestions will be appreciated.