3M Marine Adhesive Sealant 5200 MAHOGANY CAULKING. A permanent solution for bonding marine substrates like wood, fiberglass, and metal, this high-performance polyurethane adhesive/sealant becomes tack free in 48 hours, completely cures in 5-7 days with no shrinkage. Tough yet flexible polyurethane polymer is ideal for deck housings, hull fittings, porthole mounting, fiberglass transoms, and underside molding. Sold by the box of 12, 10 oz cartridges.