Greetings- I have a carbureted Mercruiser 260 with appox 150 hours in 6 years SMOH. Boat had been layed up for a few months, but started her up in the rack every 4 weeks or so. Splashed her yesterday and all ran fine, cruised about 17 mph, 2500 RPMs for maybe 10 minutes. Goosed the throttle to run her up a bit (about 3/4 throttle) for about a minute with outdrive trim up a tad, then I backed her down to a slow cruise and finally to an idle. Upon attempting to get back on a plane, I heard a really bad knocking sound almost like detonation, but more metallic and solid sounding. There is a noticible vibration below 1500 RPM, and now whenever I try to get up on a plane, the knocking comes back. There is no knocking below 1500 RPMs.
I don't think it's a stale fuel issue, because everything was OK until after I ran the throttle up.
I am thinking it may be the U-joint on the outdrive? I had salt water in there a couple of years ago and had to have the gimbal bearing replaced because of corrosion- could the clues above lead to this as a suspect? I would hate to think it's something in the bottom of the engine ($$$). Thanks for any assistance....
I don't think it's a stale fuel issue, because everything was OK until after I ran the throttle up.
I am thinking it may be the U-joint on the outdrive? I had salt water in there a couple of years ago and had to have the gimbal bearing replaced because of corrosion- could the clues above lead to this as a suspect? I would hate to think it's something in the bottom of the engine ($$$). Thanks for any assistance....
