Dear Boat Doctor,
We own a 1983 Catalina 30 and recently resealed the windows. We removed the windows, completely cleaned all residue and applied butyl tape to reseal. Now, that butyl tape has created a mess on the fiberglass and I want to maintain the seal on the windows while protecting the boat from additional black blobs and streaks. Of course, we had people on the cabintop as "rail meat" during a regatta so a lot of this is caused by the movement of people (picking up excess sealant and carrying it on their shoes). I need a solution to the problem.
Patricia Holladay
via sailingmagazine.net

Dear Patricia,
Butyl tape is a great bedding compound, it is easy to use, cheap, and as you discovered it never hardens. Typically this softness is a benefit, if the bedded part moves under load the seal is not broken, but if the butyl is exposed it will track around.
I would start by cleaning up the tracked tape with mineral spirits, it should wipe up pretty easily. It sounds like you have a lot of excess butyl tape squeezed out of the windows, I'd scrape that back with a plastic scraper as much as you can and wipe up the rest with mineral spirits.
This should take care of the problem but if you need to seal off any of the tape you can use a marine sealant. If the sealant is up against any plastic be sure to use a plastic-safe sealant, as some sealants are hostile to plastics.