Sounds like a butyl caulk compound to me. Mine wasn't dry after over thirty years.
Replaced all of mine with butyl tape. Same as the caulk just easier to work with. A moderator on sailboatforums.com sells it. Screen name of mainsail or mainesail, he has a tutorial thread I posted here a few weeks ago. I can't find it now as I'm on my Android.
It's easier to fool people than to convince them that they've been fooled - Mark Twain