-- Last Updated: Jul-18-08 12:39 PM EST --
The problem is that it bonds poorly, which is why you can peel it off and it leaves a residue the prevents anything else from stick to the surface. While silicone is fine for caulking bathtubs, it's worse than useless in a kayak. Contact cement or adhesives like Lexel work much better and don't have the drawbacks of silicone.
Personally, I use GOOP or Lexel for installing foam bulkheads and similar applications where the joint will be under pressure while it cures, but contact cement gets the nod for everything else. My favorite contact cement is Weldwood Gel, as it works as well as the liquids, but doesn't run all over the place. When installing foam seats, I'll usually run a bead of Goop around the edges after installing the seat with contact cement. That seals the the seat-to-hull joint and prevents water from getting in under the seat.