<< A polyurethane adhesive/sealant (such as 3M 5200) will not harm gelcoat.
At
least it won't soften it in any way.
However, I would think very carefully before you use polyurethane
sealant/adhesive/bedding compound -- whatever you bed with polyurethane
sealant will NEVER come off without pulling chunks of the fiberglass and
gelcoat with it. If you use 5200, the thingy is attached absolutely
permanently. >>
Not quite so...
There is now a product called 5210 polyurethane sealant remover that melts
the stuff away.
SF