Get the stuff in a can called "Goop Off" and a straight razor blade.

Douse a rag with some goopoff and rubs down the stickers one at a time, wait 30 seconds and rub it down again. Wait another minute for it to get behind the sticker then carefully use the straight blade to peel back the sticker. Be careful not to nick the gelcoat with the corner of the razor.

Works well for removing pinstripes too.

And there are tons of Gcats out there. Good boats.