The reason I think it's the flywheel is because I/and my mechanic, have ruled everything else out. From prop, to prop shaft, gimble bearing, u-joints, plugs, wires, timing, distributor, ignition coil, compression, and harmonic balancer. I had starting problems last year and replaced the starter and when I did I noticed it was a cheap aftermarket one that was in there. So when I noticed that I figured it's more than likely that the starter, ring gear, flywheel had been messed with. Now I know the ring gear is separate but I don't know the story from the previous guy, for all I know he had a buddy with a V8 flywheel kicking around and said it works no problems so they had it put on. I took it to my marine mechanic and he concluded the exact same thing. My thrust bearings/cam bearings are just inside the tolerance line for wear, so I'm at one of two things left. Either for some reason my timing chain skipped a tooth or is unaligned, (but i'd think that could be made up with rotating the distributor) or the flywheel is the wrong flywheel. I talked with a guy from australia who bought a used MPI and had it put in, and he had the exact same vibration at the exact same RPM's and he didn't know what was going on. He took it back to where he got the engine and they concluded it was the flywheel and swapped it out. Since then he said it's perfect now. So all of that combined, leads me to believe it's the flywheel. I buy and sell boats constantly, so I'm selling it anyway in the spring, but would like to calm the vibration first. I'd rather not pull the engine and swap the flywheel on a boat that i'm selling anyway. I also don't want to sell a piece of crap to somebody. Runs perfect except for a vibration at 2500-3000rpm. I like to sleep carefree! haha! Thoughts?