I tryed the seafoam and it did cut some of the carbon out of the engine. I decided to pull the head off the engine to clean it, Found the ring stuck in carbon. I ordered a Frank Bowman ring a little oversize to fit the block. Cleaned the engine and sanded the head and replaced the ring with Bowman ring. I have about 1/2 gal. of fuel run in it and it has picked uped to 7300 RPMs. I think it will keep getting better as the ring seats. I plan to try other props and will post the results. Wayne M.