Marine Caulking & Adhesives

Marine Caulking and Adhesives

Caulks and sealants serve three main purposes on boats. First, they are used to create a waterproof seal between two or more materials. Second, they are used when joining two or more pieces, often in conjunction with mechanical fasteners. Third, they are used to isolate one piece from another to reduce noise, vibration or in some cases electrolysis. The flexibility and adhesive strength of a sealant or caulk varies based on its formula. Marine grade sealant cure times can vary from a few hours to more than a week.

Considerations

When selecting a marine caulk, first consider how the caulk will be used. For more on this, please read our West Advisor article, How to Select Sealants and Caulk, which includes a helpful chart that explains various West Marine and 3M compounds and the best use for each.

Polyurethane

If you are looking for adhesive strength, reach for a polyurethane marine adhesive/sealant. Polyurethane boat adhesive/sealants have great adhesive strength and can be used for above- and below-the-water-line applications including hull to deck joints and thru hull fittings. Not recommended for bonding ABS, Lexan or other plastics.

Silicone

Silicone is one of the most flexible and versatile boat caulk types. It is often used for isolating metals to prevent electrolysis or reduce vibration. It works well for sealing plastics but does require compression to maintain its adhesion. It’s important to note that tidy caulk lines are vital when working with silicone as it cannot be painted over. Silicone is a good choice for sealing plastic windows and port holes.

Polysulfides

These versatile rubber sealants come in one- and two-part formulations that work well for bedding teak to fiberglass. Examples include teak decks, cockpit combings and teak handrails. While two-part systems can require more patience to apply, their overall cure time may be shorter than one-step products. The adhesive quality is similar for both. Caution: While polysulfide caulk can be used to bed certain plastic fittings, such as those made from epoxy, nylon or Delrin, it should not be used to bed many other types of plastic items—which it can melt. Items that polysulfide will damage include acrylic windshields, polycarbonate portlights and fittings made of ABS or PVC plastic.

Polyether

A great choice where chemical resistance is required, polyether is not affected by teak oil, or cleaners. Remains permanently flexible and can be sanded and painted over. Certain formulations however will attack some plastics; so be sure to read the label carefully before using for sealing Lexan windows or plastic hardware.