My thoughts -- not ever had a encapulated keel, myself:

When it came out of the water (a couple of years ago), was it draining a bunch of water out or was it just a little wet or?

If you have pockets of water that freezes and thaws, then I'd think you actually exacerbated the issues of delamination. If you have some surface cracks (from differenential expansion or flexure or whatever, then I'd fair and fill those. Put the boat in the water an move-on until you next examine it.

However, if its suffering from serious necrosis now, then you have little choice but to do a more significant repair work. That work would probably include taking a lot of the fiberglass off and rebuilding what "was" there.

Do you have some pictures you could post of the situation????