They recomended rebuilding both carbs, tuneup, and sync the carbs, Clean compresion valves. I was told the compresion valves release extra compression when the engine is idleing and makes it run smoother at idle . I was told they plug up with carbon and stop working. I just called my boat guy he told me he has a 2002 merc 2 stroke new I can pickup for $2000.00 plus tax . I am thinking bout making a trip their this weekend.