I recently purchased a boat with twin Honda 225's. The Boat ran fine until last week when I got a buzzer alarm on the port engine while idling. It apparantly is the 02 sensor. The dealer researched the engine's history and found that both engines had been serviced in 2008 with the exhaust pipe kits according to Honda Service Bulletin #56. This obviously has not resolved the problem. In any case, all I can do is replace the 02 sensor (it's under warranty) and hope for the best.