Yes but tighten SLOWLY. I often stand on the hatch frame to compress the butyl then take a turn then stand, take a turn etc.. Our hatches were bedded in 1979 with butyl. I removed one this summer ans it was still 100% bone dry decided not to touch the other one..
I have found on every occasion that i need to that gasolene or alcohol, either one will remove cured or uncured silicone..... although removing cured silicone is not an instant process, if you have the patience to keep the solvent applied, it will be softened and dissolved or granulated by either fluid...Amen! Though there are some uses for it, specifically Beckson products and acrylic or polycarbonate lenses but the stuff contaminates the heck out of gelcoat. Cured silicone laughs at MEK, paint thinner, acetone, mineral spirits, gas, toulene etc. etc.. About the only thing that will get silycone off your gelcoat is a nuclear bomb..
It may appear to be removed but the contamination of the gelcoat is still there. Try to paint over it and you'll see what I mean...
That's why a) I used to put off leak repairs for a long time (to collect up enough leaks and/or time to get into it), and b) I switched to butyl tape, which I got from Maine Sail - I keep it in a zip-lock bag, and it's always ready to go. Small repairs can be done without trashing a new tube of goo, and there's no mess. I'm also more likely to take on small leaks when I'm thinking about it, so little by little, the boat is becoming dry.
