My previous boat, a Kells 28, had a fin keel with internal ballast...i.e. the fiberglass hull also included a fiberglass fin keel, and the cavity of the keel was filled by a mixture of resin and lead shot to get the ballast. In the 70's this was considered a good way to prevent leaks at keel bolts on bolt on keels and probably a more expensive method of construction. One year, I discovered ,at a haul out for semiannual bottom job, that the keel was weeping about a foot above the bottom near the trailing edge. (Actually, I knew something was wrong since the keel sump would gain water over time but the auto bilge pump kept things in check). From your description, it sounds as if you may actually have this type of keel assembly instead of the more normal (today) bolt on keel (i.e. bolt on keels are generally one piece castings of lead or iron). The yard ground open the the area that was weeping and a bit of the trailing edge. They put a heat lamp on it day and night for almost a month and eventually it stopped weeping and was dry enough to use epoxy to rebuild the ground away areas. I never had a problem with it after that. The cost was not very high and generally it was a happy ending. Apparently there was a void in the fiberglass/ballast mix, and probably at the previous haul out, the boat may have been set down unevenly with too much force on this hollowed out area in the keel, causing a fine crack, which allowed ingress of water when the boat was in the water. Hope your repair job works out as well.