[Ryank]

There are several great strippers out there on the market that are fiberglass safe. I would reccomend that, you may need to do several applications but eventualy it would get the job done, you may have to sand at the end but should be minimal. I can say Don't try to pressure wash it off as it will gouge holes through the Gelcoat, also if you decide to sand wear a mask, breathing too much bottom paint dust can make you very very ill for a long period of time.
Lots of things to do with the transom I went all out and enclosed my entire transom and put a bracket on, but was very pricey.