BoatUS Magazine's Mark Corke takes you through the steps for how to repair boat gelcoat. This gel coat repair DIY if you need to fix a boat ding, crack, or scratch is not difficult and could save you a lot of money by doing it yourself and still get professional results. The process for repairing gelcoat on a boat (on flat surfaces) starts by preparing the area to be repaired by thoroughly cleaning with soap and water and then acetone. Use a Dremel with a burr bit to open up the repair area, then vacuum the dust. Mix the gelcoat according to manufacturer directions and add any coloring to match your boat's gelcoat. Tap it into the repair and overfill. Once dry, use wet sandpaper to sand it flush with the surrounding surface. Use cutting compound then finish with a little wax to finish it up.