My bronze shaft log started leaking. Upon removal (tapped it off from the inside; it had very little sealer, mostly just a gasket) it shattered into bits. The first picture is after removal of the old shaft log which was a simple flange with a 1 1/2 O.D. tube in the middle of it. The best advice I received seemed to be to glass in a new fiberglass tube. I found a great 1 3/4 O.D. resin based tube here:

http://www.amalgacomposites.com/amalga-black-amalgon.asp

I put two coats of epoxy on the tube and sanded it. I dry fitted the shaft on, with the tube held perfectly centered around the shaft using plumbers putty in both ends. I then tabbed the tube in with a glob of 105 resin mixed with 404 filler. You can see it at this stage in the second picture. After the resin dried, I removed the shaft and applied five or six successive layers of 404 filled epoxy inside and out around the tube, sanding off with a dremel sanding drum in between each layer as needed. I washed off the epoxy with soap and water before each sanding but only if the epoxy has completely cured, otherwise you can just apply another layer. I followed the instructions here for epoxying technique:

http://www.westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

Lastly I applied a layer of fiberglass on the outside and sanded it down smooth with the hull. You can see it almost ready to paint in the second to last picture. Painted with bottom paint. If I had more time Id have put a few less layers of filler/resin and a few more layers of fiberglass on the outside. Id have painted with polyurethane before the bottom paint. No biggie, I figure.