How to Repair a Scratched Fiberglass Boat

By Kimberly Johnson

Many modern boats are manufactured out of fiberglass because of its durability and water resistance. However, while fiberglass boat hulls are long lasting, they are susceptible to scratches, especially on the outside where they hit docks, rocks and other obstructions. Repairing fiberglass scratches requires only minor abrasion if they are shallow. Deeper fiberglass scratches require a more extensive repair, but boat owners can typically perform the process themselves without professional assistance.

List of Items Needed

  • Water
  • Hand-held rotary tool
  • 150-, 220-, 400-, and 600-grit sanding accessory
  • Flat, dull blade
  • Cloths
  • Styrene
  • Paste form gel coat with hardener
  • Paint stirrer or Popsicle stick
  • Flexible, plastic putty knife
  • Clear plastic
  • Painter's tape
  • Rubbing alcohol
  1. Dampen the scratched area of the boat. Install a 200- to 600-grit sanding accessory onto a hand-held rotary tool. Move the wheel over the scratch in circular motions using only gentle pressure. Continue for 10 to 20 seconds to see if this removes the scratch. If the scratch is still present, continue with the removal process.

  2. Insert the blade of a flat, dull blade into the the center of the crack and pull it along the bottom of it two or three times with firm pressure. This widens the crack slightly allowing for a more secure bond.

  3. Open a bottle of styrene and apply 1 tsp. to a cloth. Wipe the surface of the crack thoroughly with the cloth to reactivate the old gel coat.

  4. Mix the gel coat with the hardener that comes with it using the manufacturer's instructions. Typically, you will add 1 to 2 percent of the hardener. Stir the mixture up well with a paint stirrer, or a Popsicle stick for small amounts.

  5. Scoop up 1 to 2 tsp. of the gel coat mixture using the flexible putty knife. Press it into the crack to fill it completely. Once the crack is completely filled, run the knife across the top of the crack to scrape off the excess. The gel coat should bulge up slightly by 1/8 inch or so.

  6. Cover the repair area with a piece of clear plastic taped along the edges with painter's tape. Allow the repair to dry for 24 hours and then remove the plastic.

  7. Attach a 150-grit sanding accessory to a hand-held rotary tool and sand the surface of the repair to smooth it until it is flush with the surrounding surface. Then switch to a 220-grit sanding accessory and dampen the surface. Sand the repair again to remove any grooves caused by the first sanding.

  8. Switch to a 400-grit sanding accessory and repeat the process. Complete the repair by sanding it with a 600-grit sanding accessory.

  9. Wipe the boat hull with a cloth to remove the moisture. Apply 1 to 2 tsp. of rubbing alcohol to the cloth and buff the repair until it shines.

© Demand Media 2011