Sikaflex 291 Fast Cure Adhesive Sealant 10. 3oz 300ml Cartridge Black. Sikaflex 291 is a 1-component, marine grade polyurethane elastomeric adhesive and sealant. Used by many boat builders, its fast cure time makes it ideal for applications where speed is important. Uses General all-purpose, marine adhesive and sealant, which may be used for light duty bonding. Sikaflex 291 has excellent adhesion to gelcoat, fiberglass, metal and wood that can be gunned or brushed into place. Characteristics Advantages Use above and below water lineResists salt water. Fast strength build-up. Paintable and sandable. Excellent bond. NSF approved for potable water black and white only . USDA approved for incidental food contact. Sikaflex 291 Fast Cure Adhesive Sealant 10. 3oz 300ml Cartridge Black. Sikaflex 291 is a 1-compo nent, marine grade polyurethane elastomeric adhesive and sealant. Used by many boat builders, its fa st cure time makes it ideal for applications where speed is important. Uses General all-purpose, ma