M_Boats: Keel Crack

I own a 1974 Montgomery 17. The boat has been out of the water for several years. I just noticed a crack in the fiberglass of the shoal keel. I'm not certain of the construction but it looks like an inner steel or iron structure may have rusted, expanded, and split the fiberglass. The crack is roughly horizontal, about midway between the hull and the bottom of the keel, about 2-feet long, and nearer the aft end of the keel. The split is nearly 1/2-inch wide. I also just noticed a bulge and hairline crack on the opposite side of the keel. Any insight and/or suggestions? Thanks. Sincerely, John Crews