J-B Weld MarineWeld is a specially formulated two-part epoxy cold weld system that provides for strong, lasting repairs for bonding different or similar surfaces, such as aluminum, metal, composites, fiberglass and others. MarineWeld sets in 4-6 hours at room temperature and is fully cured to a dark grey colour in 15-24 hours. Once cured, it can be shaped, tapped, filed, sanded and drilled and will retain its strength above or below the waters surface. MarineWeld has a 1:1 mixing ratio and tensile strength of 5020 PSI.