I have a 2006 Crest 2 with a Mercury optimax 115 (160hrs), according to the dealership the cause of the piston deteriorating and cylinder wall scaring was due to pre-detonation. Only one of the piston did this and the other two cylinders are fine, Mercury came and looked at the engine. According to Mercury this is my fault for using ethanol based gas and that they refuse to do anything to resolve this issue. I have had the o-ring for the fuel system replaced twice last year and was never notified until the last incident in October 2009 that I was to use a fuel stabilizer. Since day one when I bought the boat the dealership has maintained the boat for me, this includes all storage and winterization. The dealership and Mercury refuse to claim any responsibility for the engine. Is anyone else having similar problems with their engines, please let me know. These are the kind of things that make you not want to be a boat owner any more!!!!!!