Repairing scratches in fiberglass?

I bought a used Old Town Stillwater a couple of years ago. I love the light weight and easy maintenance (compared with the wooden version it replaced) However, the bottom is heavily scratched with several fairly deep gouges. is it possible to have the gel coat repaired? Expensive? Has anyone ever bothered to do this?

Definitely possible. If the scratches are through to the laminate they should be repaired. If just cosmetic they can be left, shallow ones may be buffed out.

How expensive the repair is depends on how good you want it to look. A DIY repair is very doable, but matching gelcoat color (especially old gelcoat) is very difficult. So it could be a few bucks for a gelcoat repair kit and do it yourself, up to hundreds of dollars (if not more) for a complete refairing and respray.