I have a 2016 Mercury CT 115 hp engine in a 21’ pontoon. It continues to run hot and cavitate at full throttle. When I back the speed down 5 mph there is no problem. The dealer first said the motor was mounted too high and dropped it one hole. The second time it was a dirty thermostat. The third time it happened they said there is a service bulletin out to replace the thermostat. I feel like I’m getting the run around. Any thoughts on this problem?