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I pulled the shaft to check the flange alignment and there was no gap at all. It also turns very easily, smoothly, and freely. I had a lovely Yanmar 3GM in another boat that was aligned by a boat yard, not realizing that on the hard, the weight on the keel deformed the hull enough that it was way out of parallel when floating. I could see it shift the engine on its mounts as I turned the shaft by hand.
I do have a pretty old two-bladed prop quite close to the keel, I half expected to see a chip out of it or a damaged zinc, but none of that has changed, and it ran smoothly before the bearing work, tho' I did not replace the flange, I just put a sealing sleeve on it.
The kicker for me condemning the forward support bearings was the loud whirring sound it suddenly made when spinning the prop in the air during my winterizing run. I shifted it to neutral, and the noise stopped, went back into gear and it was gone. Maybe this is normal and unrelated.
In the rev gear video (see attachment) I see what looks like a babbit bearing with a large retaining clip in the outer clutch drum that rides on the end of the crankshaft, as well as the tip of the tail shaft, but no instructions on removing either bearing, as well as no listing for that drum bearing in the catalogue.
My manual discusses disassembling the gear case to replace the disks etc. and there is instructions in the engine rebuild section about removing the rear housing and getting the gear case out, but also mention of an idler shaft and bearing that I can't identify.
My rear bearing was really badly shot, so I've also presumed the forward bearing would be in similarly poor shape. The way I can imagine these forward bearings causing this vibration is if they are so worn that the gear case is able to shift off off its centerline.
I'd hate to tear it all down and replace the pilot bearing only to find I did not solve it, either because it was that drum bearing or something like a bent shaft or prop. Hmm?
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