Mast boot sealer???
I replaced my old rubber wedges with SparTite last year. It did solve the problem of water getting in around the mast. (I still use a Sunbrella cloth boot, since SparTite doesn''t like UV.) Follow the instructions carefully. You need to apply petroleum jelly to anything you don''t want SparTite to stick to (sort of a mold release.) I haven''t unstepped the mast yet, but theoretically, the SparTite will stick to the mast. When the mast is stepped, it should be in the right spot.