3M 4200 Fast Cure Cartridge 10 Oz.

When you need a marine sealant that strikes the right balance between holding power and future serviceability, 3M 4200 Fast Cure is the answer. Unlike the permanent bond of 3M 5200, the 4200 formula is engineered to be roughly half the strength — strong enough to form watertight, weather-resistant seals, yet manageable enough that bonded parts can be separated down the road without destroying the substrates. This makes it a practical choice for hardware that may eventually need replacing, such as cleats, hinges, porthole frames, and rub rails.

The fast cure formula dramatically reduces downtime compared to standard polyurethane sealants. It skins over in 1–2 hours and reaches full cure in 24–48 hours at a quarter-inch depth, so you can get back on the water sooner.

Versatile Marine Bonding and Sealing Applications

3M 4200 Fast Cure adheres well to a wide range of marine substrates, including wood, fibreglass, gelcoat, most plastics, and metals. It forms reliable seals both above and below the waterline, making it suitable for a broad spectrum of jobs around your boat.

• Bedding deck hardware such as cleats, stanchions, and hinges
• Sealing thru-hulls, hatches, and porthole frames
• Bonding fibreglass deck to fibreglass hull
• Sealing rub rails, trim, and mouldings
• Trunk joints, stern joints, and strut-to-planking seams
• Wood-to-fibreglass bonding
• Electrical assembly sealing

How 3M 4200 Fast Cure Works

3M 4200 Fast Cure is a one-component, moisture-curing polyurethane. Once dispensed from the cartridge, it chemically reacts with ambient moisture in the air to crosslink and form a permanently elastic, rubbery seal. The cured sealant absorbs stress from shock, vibration, and the natural swelling and shrinking of marine substrates — critical qualities in a harsh marine environment.

The product has a caulkable, non-sag paste consistency, so it stays put in both vertical and horizontal seams. It remains workable for tooling with a spatula or tongue depressor after application. Once cured, 3M 4200 Fast Cure is both sandable and paintable, though it is recommended to test paint compatibility beforehand, as some solvent-based marine paints may not cure properly over this sealant.

Specifications

• Product Type: One-part, moisture-curing polyurethane adhesive sealant
• Cartridge Size: 10 oz. (1/10 gallon)
• Available Colours: White (#27069), Black (#27204)
• Tack-Free Time: 1–2 hours at 73°F (23°C) and 50% RH
• Rate of Cure: 3/16" (4 mm) per 24 hours at 73°F and 50% RH
• Full Cure Time: 24–48 hours at 1/4" depth
• Shore A Hardness: 40 (ASTM C661)
• Tensile Strength: 180 psi / 1.24 MPa (ASTM D412)
• Elongation at Break: > 400% (ASTM D412)
• Service Temperature Range: -40°F to 190°F (-40°C to 88°C)
• Application Temperature Range: 40°F to 100°F (5°C to 38°C)
• Consistency: Caulkable, non-sag paste
• Solids Content: Approximately 100%
• Density: 1.18 g/ml (approximately 9.75 lb/gal)
• VOC Content: 36 g/l (3%)
• Shelf Life: 12 months from date of manufacture (cartridges, stored below 25°C / 77°F)
• Overlap Shear Strength — Fir: 165 psi (11.6 kg/cm²), cohesive failure
• Overlap Shear Strength — Cold-Rolled Steel: 125 psi (8.8 kg/cm²)
• Overlap Shear Strength — Stainless Steel: 100 psi (7.2 kg/cm²)
• Overlap Shear Strength — Aluminium: 100 psi (7.0 kg/cm²)
• Overlap Shear Strength — Fibre-Reinforced Plastic: 165 psi (11.6 kg/cm²), cohesive failure
• Overlap Shear Strength — ABS: 100 psi (7.0 kg/cm²)
• Overlap Shear Strength — Polycarbonate: 100 psi (7.0 kg/cm²)
• Bead Coverage (1/4" bead): 31.6 lineal feet per 10 oz. cartridge
• Bead Coverage (1/8" bead): 126.2 lineal feet per 10 oz. cartridge
• 3M Part Numbers: 06560 (White), 06564 (Black)
• NFPA Hazard Ratings: Health: 2, Flammability: 1, Instability: 0

Key Features

• Fast cure formula — becomes tack-free in 1–2 hours and fully cures in 24–48 hours, minimising project downtime
• Removable bond strength — approximately half the strength of 3M 5200, allowing future disassembly of hardware without substrate damage
• Watertight seal above and below the waterline — protects joints and hardware from water intrusion in all conditions
• Permanently elastic cure — absorbs stress from shock, vibration, swelling, and shrinking to maintain seal integrity
• Bonds dissimilar materials — adheres to wood, fibreglass, gelcoat, metals, and most plastics in a single product
• Non-sag paste consistency — stays in place on vertical and overhead seams without running or dripping
• Sandable and paintable when cured — allows for a finished appearance that blends with surrounding surfaces
• Wide service temperature tolerance — performs reliably from extreme Canadian winter cold through summer heat
• One-component, no mixing required — dispenses directly from the cartridge with a standard caulking gun
• 100% solids formulation — no shrinkage during cure for a consistent, reliable seal