Product Listing
Marine Sealant & Caulk
Marine sealant and marine caulk are essential for sealing, bonding, and protecting boats against water intrusion. Designed to withstand constant moisture, UV exposure, vibration, and temperature changes, these products help prevent leaks, corrosion, and structural damage.
Whether you're installing deck hardware, sealing thru-hulls, bedding rails, or performing routine maintenance, choosing the right boat sealant ensures long-lasting performance in harsh marine environments.
Marine Sealant vs. Marine Caulk: What’s the Difference?
While the terms are often used interchangeably, marine sealants and marine caulks serve slightly different purposes.
- Marine Sealant: Designed for bonding and sealing; often stronger and more permanent
- Marine Caulk: Typically more flexible and easier to remove for future service
The right choice depends on whether the application requires a permanent bond or a removable seal.
Types of Marine Sealants & Caulks
Polyurethane Marine Sealant
Polyurethane sealants provide extremely strong adhesion and are commonly used for permanent installations.
- Ideal for below-waterline applications
- Excellent strength and durability
- Harder to remove once cured
Silicone Marine Sealant
Silicone sealants offer excellent flexibility and UV resistance, making them ideal for removable components.
- Easy to apply and remove
- Great for above-waterline use
- Not recommended for structural bonding
Hybrid & Silicone-Polyurethane Sealants
Hybrid sealants combine strength and flexibility, offering strong adhesion with easier removal than traditional polyurethane.
- Balanced performance
- Reduced cure time
- Versatile for many marine applications
Above vs. Below Waterline Applications
- Above the Waterline: Deck hardware, rails, hatches, windshields, trim
- Below the Waterline: Thru-hulls, transducers, seacocks, underwater fittings
Always confirm that a marine sealant is rated for below-waterline use before applying it underwater.
How to Choose the Right Boat Sealant
- Permanence: Will the part need to be removed later?
- Location: Above or below the waterline
- Material compatibility: Fiberglass, aluminum, wood, or plastic
- Cure time: Standard vs. fast-cure formulations
Marine Sealant & Caulk FAQ
What is marine sealant used for?
Marine sealant is used to seal and bond boat hardware, fittings, and joints to prevent water intrusion and corrosion.
Can marine caulk be used below the waterline?
Only caulks specifically rated for below-waterline use should be used underwater. Always check the product specifications.
What’s the difference between 3M 4200 and 5200?
4200 offers strong adhesion with easier removal, while 5200 creates a permanent bond intended for long-term installations.
How long does marine sealant take to cure?
Cure time varies by product and conditions, ranging from a few hours to several days.
Can I paint over marine sealant?
Some marine sealants are paintable after curing, while others are not. Always confirm before applying paint.