Over the Memorial Day weekend, while sailing east of Cutts Island in Carr Inlet, the mizzen boom gooseneck broke while I was sheeting in the mizzen. Luckily, I was able to get the boom under control and the sail down before any further damage occurred. This was not a hard sail, and there had not been a lot of strain on the fitting.
Inspection of the failure showed that the fitting had been broken for a long time, and that it was apparently only the corrosion products which were holding it together. In a failure like this, there will usually be a small area of bright metal - the last piece of sound metal which was holding things together when the break finally occurred. Not so here - it is ALL corroded.
I purchased a new gooseneck fitting from a local Le Fiell distributor (the company that made our spars) - it is a stainless investment casting.
Getting the axle portion of the old fitting out was a very tough job. It was corroded into place solidly - it would not allow the boom to rotate. First I simply tried to drive it into the boom - not a chance, even when using my 6 lb hand sledge. Next, I drilled a series of holes right next to it, all the way around, trying to release the tension on it. No chance.
Finally, using a sabre saw, I cut all the way around the portion of the casting containing the stainless axle. It was an ugly job, costing 3 blades, but finally it was out.
Next, I had a piece of 3/8 aluminum drilled to accept the gooseneck fitting (at that time, I didn't have any drill bits large enough), and trimmed it to fit on the end of the boom. Then, I drilled and tapped holes in the remaining portion of the casting, and overdrilled holes in the plate to match. After countersinking, the plate was screwed onto the remains of the casting.
After attaching the fitting to the plate, the plate is permanently attached to the end of the boom using the screws, locktite and 5200. After a final touchup with the angle grinder, it is painted, and is as good as new (well, maybe better...)