3M’s Marine Adhesive Sealant is the preferred choice for sealing masts. It goes on smoothly, won’t sag, and remains workable for up to 4 hours. The seal is extremely strong and retains its strength above and below the waterline. The sealant provides incredible adhesion, yet stays flexible after it’s cured. It becomes tack-free in 48 hours; completely cures in 5 to 7 days with no shrinkage. Clean up with kerosene or mineral spirits. 3 oz. tube. White.