My engine is currently being worked on by a Yamaha mechanic with the ultrasonic cleaner. All tolled it will have cost me about 1300 dollars in repairs this year, none under warranty. I have used ring free religiously and run the boat almost every week. I buy the gas from I high volume station and yes it has E 10. I have a Racor filter and no water appears in the bowl. I am thinking about repowering and I may go with a Honda 50 which is fuel injecte and weighs less than the Yamaha F40a. The HPX 15 is only rated for a 40 HP max but I sometimes like to make long runs and my top speed is only about 31 wide open. Any opinions on exceding the HP rating on the boat but not overweighing the boat.