J-B Weld J-B MarineWeld™ is a specially formulated two part Cold-Weld™ adhesive system that provides strong, lasting repairs for bonding different or similar surfaces, such as metal, composites, fiberglass and others. MarineWeld™ sets in 20 minutes at room temperature. At full cure, its color is white. It may then be shaped, tapped, filed, sanded and drilled, retaining full strength above or below the waters’ surface. MarineWeld™ has a 1:1 mixing ratio and tensile strength of 2350 PSI.