3M Marine Adhesive Sealant Fast Cure 4200FC (06560) – Flexible, Watertight Sealant for Boats & RVs (295 mL Cartridge)

Overview

3M Marine Adhesive Sealant Fast Cure 4200FC is a moisture reactive, one part polyurethane sealant designed for demanding marine environments. It bonds to wood, fiberglass, gelcoat, plastics, and metals, delivering a flexible, watertight seal on joints and boat hardware above and below the waterline.

The formulation remains elastic under stress, accommodating movement from vibration, swelling, or temperature shifts. It resists weathering and salt exposure, helping maintain a steady seal across years of outdoor use. Available in cartridge and sausage packs to fit different installation needs and workflows.

Key benefits

• Cures fast; one part, no mixing required, typically reaching handling strength in about 24 hours
• Seals above and below the waterline, ideal for joints, rub rails, access plates, and other shaded areas
• Long lasting formula uses tough polyurethane to resist weathering and salt water
• Stays flexible and resistant to cracking or peeling during vibration or structural movement
• Disassembly without damage; medium strength allows bonded parts to come apart after extended use
• Designed for industrial or occupational use; not intended for consumer application

Applications and use cases

Commonly used for fiberglass deck to hull joints, wood to fiberglass connections, portholes, deck fittings, rubrail attachments, screw hole sealing, and stanchion supports. The product’s versatility supports a range of marine and transport projects where a flexible, durable seal is desirable.

Usage guidance

Prepare surfaces by cleaning and lightly dampening where appropriate. Apply an even bead along the joint, then cure with ambient moisture. No mixing or special equipment is required, and you can choose between cartridge and sausage formats to suit your workflow. Note that this product is intended for professional use and should be handled according to safety guidelines.