I have no idea what could be wrong with the boat. I have fought this rpm issue for a long time, there are almost no people around that do carb engines so I have to identify the problem then have someone try to fix it. Each time they start with a tuneup so its had 6 in 7 years and I only get about 15 hours a year on it.While doing this post I continued to research, I may have found the problem and have ordered a throttle roller.Crossing my fingers. If not its time for a new prop