Hi Will,
Thanks for your comments. Good discussion. I should probably clarify what I mean by “permanent.”
For a 30-year old boat, I would say that even “permanently” bonded elements like the keel should be inspected for integrity and overall condition.
In the case of the original poster, it seems like someone glassed or epoxied over the keel joint. In doing so, they changed a joint that, because of the 5200, may have had some allowable flex in it; to a rigid, inflexible joint. It’s hard to tell from the photo whether the crack is superficial, caused by some lateral movement of the keel as the boat heeled, and for which the brittle epoxy skin was too thin to resist, or there was some impact damage (for which other evidence, such as a gouge in the keel, should exist).
In any case, I would advise that the poster drop the keel, inspect the integrity of the keel sump, and reinforce or repair if needed (I would probably reinforce in any case, given the problems with other 302s we’ve seen). With the keel off, I would inspect the condition of the keel bolts, and repair those if necessary.
Once all repairs and reinforcements are complete, I would reattach the keel with 5200. Why? Because at this point, I would take the strength and integrity of 5200 over the accessibility of 4200. If done properly, I would expect a 5200 joint to last at least another 15 years (based on how long the original seals/joints have lasted). No inspection required unless water starts seeping in from the keel joint, or if water seeps from the outside after hauling. In either case, that is an indication the seal has failed and some repairs are necessary.
If you use something like 4200 to bed the keel in order to make repairs easier, that would be like a self-fulfilling prophecy… using 4200 would I believe make it much more likely that you would be looking at another keel stub repair or failure in the near future. And that is one prophecy I would definitely not want to come true.
I don’t think it’s a question of the bolts being strong enough. Unless there is significant corrosion, they will always be strong enough to hold the keel. Again, unless there is corrosion, I don’t think I’ve ever seen a case of keel bolt failure. It’s always the fiberglass sump that fails, pulling away from the rest of the hull by the bolts. So by transferring and spreading the stress to a broader surface area, using a powerful adhesive like 5200, the joint is much stronger and less likely to fail. I’ve seen keels bonded with 5200 survive a hard impact on a granite reef. The keel was damaged beyond repair—wing bent back like putty—but the keel sump was undamaged and no water in the boat. Relying on only the fiberglass under the keel bolts I believe make it more likely that will rip out from the bottom in the case of an impact, leaving you with a pretty big hole in the bottom of the boat.