Why not silicone to seal?

I’ve read in several threads to NOT use silicone as a sealant/adhesive on kayaks. Is there a particular reason for this? Does it have some sort of reaction with the polyethelene (did I spell that right?)?

My factory installed floatation (read- foam chunk) keeps coming out, despite me using a much longer screw to hold it in. The original adhesive they used at Wilderness Systems didn’t make it through 2 paddles. I was going to squirt some silicone caulk on the top & bottom before re-installing it this time, but I see many suggestions to not use silicone for bulkheads…

Is there a real reason to not use silicone, or is this one of those “buy our expensive specialty product” ploys?


two reasons:

– Last Updated: Jun-10-12 9:44 AM EST –



Two. Silicone is a broad based group of chemistry that varies tremendously. The original GE silicone was good but in efforts to make it do more things, some silicones just don't stick well but a are good for flexibility or mold resistance or filling cracks.

You might use silicone and it might work perfectly. The unanimous choice is usually Lexel. Whatever you use, make sure the surface is clean. You can use alcohol. Acetone cleans plastic boats well (actually can dissolve it) but it can melt a foam bulkhead.

+1 on Lexel
You’ll always be happy with its results if you apply it well.

There’s a suburban myth that use of
silicone will foul the surface of a “glass” boat so that other adhesives or repair resins won’t stick. But this can’t apply to silicone “rubber.” It might apply to silicone seal saver products or to 303, but no one has said so.

The original GE silicone “rubber” was good for gluing broken dishes, but not much good as a glue for other purposes. If I were trying to seal screws on poly kayaks, I might use Aquaseal or a similar urethane.

Silicone sealers DO leave residue
Silicone leaches from the sealer into the surface of the deck/hull/whatever and unless it is removed completely, it adversely affects the bonding of other materials. It can be removed with hexane or proprietary cleaners, but they’re both rather difficult to find and may be expensive.

In general, silicone sealers produce rather weak bonds compared to products like Lexel, so there’s not much point in using them and risking surface contamination.

I have used Shoe-Goo to glue things
in and on my poly kayaks and has held extremely well. The only problem is to remove it takes a razor blade.

Heptane (C7H16)

– Last Updated: Jun-10-12 8:49 PM EST –

You can buy it as "Bestine" rubber cement thinner in office and art supply stores for about $12 a pint. Not hexane, but close.

Ants Love It
And attack my silicone seal immediately, so my boat leaks again.