How to repair boat gel coat scratch

Boat owners understand the importance of maintaining their vessel's appearance, especially when it comes to the fiberglass exterior. Over time, the gel coat, a protective layer applied to the fiberglass surface, may develop cracks, spider cracks, or chips due to wear and tear. Thankfully, with the right tools and knowledge, quick fixes are possible. In this article, we will explore what a boat gel coat is, common types of gel coat damage, and how to use a boat gel coat repair kit to restore your boat's fiberglass surface efficiently.

What is a Boat Gel Coat?

A boat gel coat is a specialized protective layer applied to the outer surface of the fiberglass hull or deck during the boat's manufacturing process. This gel coat not only enhances the boat's appearance by providing a glossy and smooth finish but also serves as a barrier against moisture, UV rays, and other environmental factors that can damage the underlying fiberglass. Over time, due to exposure to the elements and regular use, the gel coat may sustain minor damages that require repair.

Types of Gel Coat Damage

  • Gel Coat Cracks: Gel coat cracks are relatively common and can occur due to impacts, temperature fluctuations, or hull flexing. These cracks can be superficial or deeper, depending on the severity of the impact or stress. Superficial cracks may not penetrate the underlying fiberglass, but they can still be unsightly and require repair.
  • Spider Cracks: Spider cracks are fine, hairline fractures that often spread out in a starburst or web-like pattern. They are usually a result of age, stress, or improper hull flexing. Spider cracks are more challenging to repair compared to simple gel coat cracks.
  • Gel Coat Chips: Gel coat chips occur when a portion of the gel coat is chipped or scratched off, exposing the underlying fiberglass. These chips can be caused by collisions, dropped tools, or other impacts.

Preparing the Surface for Gel Coat Repair

Before applying a new gel coat layer using a boat gel coat repair kit, it's essential to properly prepare the damaged area to ensure a successful repair. Follow these steps:

  1. Clean the Area: Thoroughly clean the damaged area using a boat-safe cleaner to remove dirt, grease, and any contaminants that might interfere with the repair process.
  2. Sand the Area: Carefully sand the damaged area using fine-grit sandpaper to create a smooth and clean surface for the new gel coat to adhere to. Be cautious not to sand too aggressively, as it could damage the underlying fiberglass.
  3. Remove Dust and Residue: After sanding, use a tack cloth or a clean, damp cloth to remove any dust and residue from the surface.
  4. Mask Off Surrounding Areas: To avoid accidentally applying gel coat to adjacent areas, mask off the surrounding surface using painter's tape.

Using a boat gel coat repair kit

A boat gel coat repair kit typically contains all the necessary materials to facilitate a quick and effective repair. Follow these steps to apply a new gel coat layer:

  1. Prep the Gel Coat Repair Mix: Mix the gel coat repair compound according to the manufacturer's instructions. Some kits may come with pre-colored gel coat, while others might require you to add pigments to match your boat's specific color.
  2. Apply the Gel Coat Repair: Using a brush or an applicator, carefully apply the gel coat repair compound to the damaged area. Ensure that the application is even and slightly overfilled to allow for sanding later.
  3. Smooth the Surface: After applying the repair compound, use a putty knife or a plastic spreader to level the gel coat with the surrounding surface. This step will help achieve a seamless finish.
  4. Let it Cure: Allow the gel coat repair compound to cure according to the manufacturer's instructions. This typically takes several hours or longer, depending on the specific product and environmental conditions.
  5. Sand and Polish:** Once the repair has cured, sand the repaired area using progressively finer grit sandpaper until it matches the smoothness of the surrounding gel coat. Finally, apply a boat polish to bring back the glossy finish.

Tips for Successful Gel Coat Repair

  • Work in a Well-Ventilated Area:** When using the gel coat repair kit, ensure proper ventilation to avoid inhaling fumes or chemicals.
  • Follow the Manufacturer's Instructions: Each gel coat repair kit may have specific instructions and curing times. Adhere to these guidelines for the best results.
  • Practice on a Small Area: If you're new to gel coat repair, consider practicing on a small inconspicuous area first before tackling more prominent damages.
  • Protect Yourself: Wear appropriate protective gear, such as gloves and safety goggles, when working with the repair compound.


Repairing gel coat damage on boat fiberglass doesn't have to be a daunting task. With a boat gel coat repair kit and proper preparation, you can quickly fix gel coat cracks, spider cracks, and chips, restoring your boat's exterior to its former glory. Remember to choose a high-quality repair kit, follow the manufacturer's instructions diligently, and take necessary safety precautions. By investing a little time and effort, you can maintain your boat's aesthetic appeal and extend the life of your beloved vessel for years of enjoyable boating experiences.