The hulls are not super thick on these boats to start with... like everyone says, you will need to do a structural repair.
If it were me, and I didn't want to do a major repair, I'd feather out the edges of the damaged area, fill any deep gouges with epoxy+chopped fibers, and then lay down two layers of 8" 12oz biaxial tape with a good epoxy laminating resin. Feather edges, fair with epoxy+lightweight filler, and then gelcoat it. It will look pretty good, be plenty strong, and will not build up any more thickness that you had before.
I would not use polyester or vinylester for this sort of repair... you will need more bulk (CSM) and a wider area (poorer adhesion) to get the same strength. The cost difference will not be that significant... I rebuilt my entire 17' Bayliner with just over 5 gallons of epoxy. You'd likely need less than a quart. No matter what resin you use, do not cheap out. You won't save yourself any significant money and the structural qualities of resin tend to be inversely proportional to the price.
This repair would likely cost me $100 or less.
