have a 1994 Bayliner 2252 Classic 4.3 lx vortec motor and the problem I am having is the engine started developing a slight knock could be heard at idle. We went fishing and was on and off plane idling boat for hours trolling.The boat ran strong it maintain 175 degree temp the whole time never got warmer than that then after moving to different fishing spot I came back down to an idle it idle for a while than quit, I was able to get it re started so I started heading back to the marina the coolant temp creeped up to 180 degrees but didn't get hotter than that.( that is unusual always maintains 175 degrees) I got to the marina and it did not want to idle and it also cooled back down to 175.
it fires right up on cold engine and idles but after it gets to operating temp starts running rough does not want to idle. fuel pump and fuel filter have been changed the impeller in outdrive was changed about three weeks ago. I also replaced the spark plugs they all looked pretty good but no 6 looked like it had a little oil on it but not real bad. coolant level and oil level are good. this boat does have exhaust risers on it. Any ideas?
it fires right up on cold engine and idles but after it gets to operating temp starts running rough does not want to idle. fuel pump and fuel filter have been changed the impeller in outdrive was changed about three weeks ago. I also replaced the spark plugs they all looked pretty good but no 6 looked like it had a little oil on it but not real bad. coolant level and oil level are good. this boat does have exhaust risers on it. Any ideas?