Caulk is Caulk, Right??

Most boats use all sorts of sealants and adhesives.  And there are tons of different types — 4200, 5200, multi-caulk, fast-set and so on, mostly special for the marine industry.  But in the galley and head, there are couple of applications for good old household silicone caulk (see my recent article about using it for temporary refrigerator lid seals) . . . and over the past couple of years, I’ve learned that there are some important differences in silicone caulk.

When we repainted our house a few years ago, we discovered that the exterior of the house had never been caulked.  So I used nearly a case of “paintable” silicone caulk prior to painting (yeah, it was fun).  Seven years of cruising had taught me a lot about using a caulk gun!

Then we did some remodeling in the kitchen and bath and the countertops needed to be caulked where they met the wall.  Since I had a tube of  caulk left over, I grabbed it and went to work.  It looked beautiful . . . for a few months.  Then it started looking dirty . . . and I couldn’t get the dirt off.  I tried every cleaner I could think of.

I took the time to learn the differences amongst 5200, Life Caulk, 4200, fast cure and so on. But I never dreamed that there were differences in plain old silicone caulk. There are!

Hmm, seems that paintable caulk means that stuff sticks to it.  And doesn’t come off.  So now I have to remove all the old caulk and use the right stuff.

So if you’re doing a galley or head project — say installing a new sink or countertop — and need some caulk, make sure it’s NOT paintable if you are not intending to paint over it.  Get the stuff that is designed to be left bare . . . and you can easily wipe any dirt or grease off it.

One final word — don’t expect the silicone caulk to be good for many other applications on the boat.  It has virtually no adhesive properties and is not heat-resistant.  Use it only to give an interior project a finished look, make a refrigerator seal, make your own nonskid or bed port lights.

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5 Comments
  • LaDonna Bubak
    Posted at 07 June 2013 Reply

    I wouldn’t recommend silicone caulk for rebedding portlights, personally. It has a frustrating tendency to break down just enough to let water in more quickly than more appropriate bedding materials, such as 3M 4000. IMO, 4000 is the best compound for any bedding job above the waterline because of its UV-resistant properties. (Never, ever, ever use 3M 5500 above the waterline!) None are easy to remove but silicone is one of the worst to remove fully, which is necessary when rebedding to get the best seal.

    A lot of people like to use silicone caulk to ‘temporarily’ fix leaks, which they fully intend to properly fix later (guilty as charged!). Ya gotta do whatchya gotta do, but just know that getting the stuff off later is going to be a biatch. I have yet to find a solvent that works really well (but I’m open to suggestions).

    That said, silicone caulk definitely has a place onboard any boat as long as it’s not your go-to sealant.

  • Lonnie
    Posted at 07 June 2013 Reply

    I here that Debound2000 is a good remover

  • Mike McCollough
    Posted at 23 September 2015 Reply

    Once silicone gets on fiberglass it is difficult to remove. If you have not removed it all and start sanding it just moves around. It is then very difficult to paint over.

  • Suky
    Posted at 02 May 2017 Reply

    The panels that line my boat refrigerator, have some small cracks at the corners and seams. What caulk do you recommend?

    • Carolyn Shearlock
      Posted at 02 May 2017 Reply

      Hi Suky! Good question. You definitely want them sealed so that moisture isn’t getting into the insulation. I’d probably be more inclined to use thickened epoxy, with my second choice being a silicone-based sealant (as would be marketed for kitchens and baths) — you don’t need adhesive as much as a flexible waterproof seal.

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