Bedding Deck Hardware: Silicone vs. Butyl Tape

Marine silicone, like our 3M™ Marine Mildew Resistant Silicone (#108016), is a readily available bedding and sealant compound. It is clear in color, works on fiberglass, wood, metal, rubber and vinyl surfaces, and cures in 24 hours. Silicone is great for use as a galley and head sealant, gasket adhesive, or bedding compound for portholes, hatches, windows, and marine hardware. Silicone seals and waterproofs while remaining flexible and is especially great for Plexiglass or Lexan surfaces.

Silicone does have a few drawbacks that you’ll want to consider. Many sailors find silicone messy and difficult to clean off your boat. To make matters worse, your boat’s gel coat is prone to absorb leftover silicone that squeezes out from under the hardware and then the silicone attracts dirt. To prevent this, the best way to clean up the silicone is to wet sand it off, rinsing your sandpaper frequently to prevent grinding the silicone deeper into the gel coat. If your hardware ever needs to be changed out, you’ll need to completely remove all of the old silicone before re-bedding, which can be a lot of work.

Silicone has a mediocre shelf life. Once a tube has been opened it will last for a year or two before drying out. A 3 oz. tube of marine silicone is comparable in cost to a 45-foot long roll of butyl tape.

Butyl Tape is a non-hardening, elastic rubber that is great for bedding applications on boats. It can be used to waterproof holes made for bimini and dodger frame fittings, snaps, awning track installation, stanchions and much more. Butyl tape is a soft, malleable material that can be easily trimmed, pressed and formed to create a water and airtight seal. It also increases adhesion with age after it’s applied, so it creates a long-lasting seal. Go ahead and really tighten your screws; you won’t squeeze out all the butyl no matter how hard you tighten the fittings.

Butyl tape is easily removed from hard surfaces without damaging the surface, even after years in the application and the same roll of butyl tape will last for years and years on the shelf.

Butyl tape also has some drawbacks and applications where it shouldn’t be used. Butyl tape will get hard in cold weather and will need to be warmed with a hair dryer if it’s below freezing before applying. Most importantly, Butyl tape can be broken down with mineral spirits, so it should not be used to bed fuel fills or vents as the fuel can damage the butyl and the seal.