When you are working on your boat, it's important that you have the right tools and supplies to do the job.  But what if you don't know what those right supplies are?  3M offers a variety of marine adhesives and sealants that are all high quality, but each type serves a different purpose and should be used for the proper application.  In this article, we will cover the main types of 3M marine adhesives and sealants, and explain the proper use for each.

Terminology

Before we dive into the specific types of sealants available, a brief overview of some terminology may be helpful. 

First, fast-cure or FC refers to certain 3M sealants that cure quickly.  These should be used for applications where you need to fix something quickly.  If the boat is going to be hitting the water soon, you will want to opt for a fast cure sealant.  These typically are completely cured within 24 hours.  The drawback is that while they will provide a strong and durable seal, they may not be quite as strong as the standard sealants that are offered.

UV stands for ultra-violet, and sealants with this designation are specifically formulated to hold their strength even in prolonged exposure to the sun.  Many standard sealants may degrade more quickly when they are exposed to sunlight for extended periods of time, but UV sealants are formulated to avoid that degradation.

Below the waterline and above the waterline refer to the location of the particular repair on the boat.  Repairs that occur below the waterline (the line where the hull of the ship first touches the water's surface) usually require a more durable sealant that is formulated for withstanding increased exposure to water.  Repairs occuring above the waterline typically require sealants that do a better job of retaining their original color and cosmetic appearance while also resisting exposure to the sun and other elements.

4000 UV - Flexible & Fast

The 4000 UV series of sealants offers a secure seal that can be removed if a repair or replacement is needed later.  All 4000 UV sealants are fast-cure, so it will usually be tack-free within one hour, and completely cured within 24 hours.  4000 UV sealants are very flexible, making them ideal for helping to minize the stress caused by shock, vibrations, shrinking and swelling.  4000 UV sealants also include UV protection that allows them to have a long-lasting life even when exposed to extended periods of sunlight. The flexibility and durability of the product makes 4000 UV sealants ideal for installing thru-hull fittings and deck hardware where a durable seal is required and where cosmetics are important, both above and below the waterline. 

3M 4000 UV Marine Adhesive Sealant3M 4000 UV Marine Adhesive Sealant

4200 - Strong But Removable

The 4200 series of 3M sealants offers a medium-strength bond that is secure when in use, but can be removed later if disassembly is needed.  4200 sealants form watertight, weather-resistant seals on hardware and in joints both above and below the waterline.  All 4200 sealants are fast-cure, so they are usually tack-free within an hour and completely cured within 24 hours.  They also are formulated with terrific flexibility for dissipation of stress caused by shock, vibration, swelling or shrinking.  4200 sealants are offered in either white or black, and in smaller tubes or in cartridges.  4200 is a great solution for a medium-strength adhesive on wood, fiberglass, gelcoat, plastics and metals.  Recommended applications include fiberglass deck to hull, wood to fiberglass, portholes, deck fittings, rubrail attachments, sealing screwholes, and stanchion supports.

3M 4200 Marine Adhesive Sealants3M 4200 Marine Adhesive Sealants

5200 - The Permanent Solution

3M's 5200 series of sealants are the right solution when you need a super-strong, permanent adhesive that stands up to the harsh marine environment.  5200 is a high performance polyurethane that creates extremely strong bonds both above and below the waterline. 5200 is used for permanent bonding of wood, gel coat, and fiberglass, and it cures to form a firm, rubbery, waterproof seal on joints and boat hardware.  There are fast-cure options which are totally cured within 24 hours, or standard 5200 options which cure in 5 to 7 days without shrinking. 5200 is offered in a variety of colors like white, black and tan, and in sizes from smaller 3 oz. tubes to 14 oz. cartridges.  Some common applications include fiberglass deck to hull, thru-hull fittings, wood to fiberglass, portholes and deck fittings, motors on fiberglass transoms, under moldings, hull seams above and below water line, and deck housings.

3M 5200 Marine Adhesive Sealants3M 5200 Marine Adhesive Sealants

Silicone Sealant - The Cosmetic Choice

3M's marine grade Silicone Sealant is a strong, high-quality sealant for above-the-waterline projects.  These silicone sealants are mildew-resistant with a non-yellowing, non-sagging formula perfect for the marine environment.  In addition, this marine sealant is high-temperature resistant and remains flexible even after years of exposure. They adhere to bare and painted metal, fiberglass, glass, non-oily woods, many plastics and abraded rubber.  Some common uses for 3M silicone sealants include electrical hatch sealing, dashboard components, port lights, and other above the waterline interior/exterior sealing. 

3M Silicone Sealants3M Silicone Sealants

While the sealants listed above cover the most popular options that 3M offers for marine projects, a variety of solutions are available.  If you would like assistance identifying the right supplies to get your project done the right way, please contact our ABYC-certified experts at (866) 388-0390 or email us at support@marinepartssource.com.  We're happy to help!