Hey boys, I have a 1996 Maxum with a 4.3L Mercruiser with an Alpha One. When I was out today I noticed a vibration above 2k RPM. No ticking, no knocking, nothing, just when I went over 2K I could feel the vibration through the boat. Again, there's no odd noises coming from any where. I stuck my head in the engine compartment while the boat was driving (somebody was driving) and I couldn't hear anything out of the ordinary, in fact it sounded great. But none the less the vibration was there. It didn't get worse when I turned, and there is no lack of power. It did get less when I opened her up a bit, but then slowing down it came back again. I did a compression test out of curiosity in april and it was 150 on all 6. That was done in my driveway just for fun. (I love to tinker) Now I've been around many many boats. I've owned over a dozen and this is the first i've come across like this. I've done gimble bearings before, but those were noisy sounding especially when turning and were pretty obvious. This is no odd noises just a vibration. Could it be the U joints maybe? I trimmed up the motor while running and the vibration stayed the same and did it again when I got home in the driveway with the same result. Or maybe, just maybe a symptom from a bad gimble bearing that I haven't come across? I thought maybe the harmonic balancer but then the engine would have a bad vibration. I put my hand on the engine while it was running and it's not shaking or doing any dancing around. Nice and steady as it should feel, yet the vibration. Because the engine feels steady that makes me believe it's in the drive somewhere. Maybe a cylinder not firing? Just remembered, the only super minor noise I did hear, was what sounded like a pulley bearing starting to go. Very, Very slight sshhhhhhh sound. I only heard that when I stuck my head in the engine bay. Thoughts?
as you are working on one problem the next problem gets in line waiting to be served.