Gelcoat is an incredibly hard two-part resin used on the hulls of many fiberglass boats, kayaks and on some aircraft. Replacing portions of gelcoat is a part of maintenance and upkeep for many boat owners accomplished on a clear sunny day. Gelcoat comes in many different colors, so it is important that you make sure and match the color of your boat's paint when choosing your gelcoat.
Determine which type of gelcoat you will need for your gelcoat replacement. For filling scratches or gouges, you should use gelcoat paste. For replacing a worn patch of gelcoat or a large area you should use resin. Match the color of your gelcoat kit to the color of your boat.
Put on your safety glasses and work gloves. Use the 220-grit sandpaper to sand down the original gel coat. If you are repairing a scratch, then use the putty knife to make the scratch into an even "V" shape by scraping away the sides until the scratch is wide at the top and narrow at the bottom. Do not sand the inside of the scratch. Apply the styrene to the scratch to activate the old gelcoat before applying the new gelcoat.
Activate your gelcoat using the hardener compound included in your gelcoat kit. Gelcoat will begin to harden in about 30 minutes, so do not mix the gelcoat with the hardener until you are ready to apply the gelcoat to your boat. Apply the gelcoat resin to the sanded area as directed with the wide paint brush if you are replacing the gelcoat over a large area. If you are repairing a scratch, apply the gelcoat using the plastic spreader. The gelcoat should bubble slightly above flush with the scratch, as gelcoat will shrink slightly as it hardens. Do not over apply the gelcoat, as it will have to be sanded down again.
Seal the area with sealing film as directed by the manufacturer. Allow the gelcoat to set for at least 24 hours before removing the sealer film.
Remove the sealer film. If you are repairing a scratch, then sand down the hardened gelcoat paste with the 150-grit sanding block. Progress to finer grit sandpaper until the repair is flush with the surface. If you are replacing gelcoat in a general area with resin, start with a finer 400-grit sandpaper and gently sand down the area until it is flat, and finish with the 600-grit sandpaper.
Dampen the clean cloth with your rubbing solution, and buff the new gelcoat area until it matches the shine of the rest of your boat. The color should be close to matching the color of the rest of your original gelcoat and will get closer in hue as it weathers.
