Howdy, I just purchased a 1996 Sea Ray 175 RB that is 18'2" and is powered by a 3.0L Mercruiser I/O. I bought the boat from an "seemingly honest" individual with between 80 and 90 hours on the motor. Well, we took the boat out for a test run prior to buying and the first thing I noticed was a slight tapping noise coming from the engine at idle. The first thing I thought was the lifters, but he assured me that he had that checked out and the shop said that it wasn't the lifters that it was just normal engine noise. What else could the problem be and is this anything to worry about? He had just spent $375.00, the weekend before I bought the boat, on normal maintenance, carb replacment, and fluid changes and assured me that everything checked normal. Don't get me wrong, the boat runs and looks GREAT, however, I am just a little worried about the tapping noise. Any help would be appreciated.