how to repair a fiberglass boat -

How to Repair a Fiberglass Boat: A Guide for Restoring the Hull

When it comes to boat maintenance, knowing how to repair a fiberglass boat is an essential skill for every boat owner. Fiberglass boats are popular for their durability and strength, but they can develop damages such as scratches or holes over time. In this article, we will provide you with a step-by-step guide on how to repair your fiberglass boat hull from the outside, ensuring it stays seaworthy for many years to come.

Understanding Fiberglass Repair Basics

Repairing a fiberglass boat requires some basic knowledge and the right materials. Before diving into the repair process, let’s familiarize ourselves with the essentials.

  1. Repairing Scratches and Small Holes:

To begin the repair process, gather the following materials: 

  • gel coat,
  • fiberglass cloth,
  • 80-grit sandpaper,
  • polyester resin,
  • hardener, acetone,
  • and clean rags.
  1. Start by cleaning the damaged area using acetone to remove any dirt or debris.
  2. Next, sand the damaged area using 80-grit sandpaper until it is smooth.
  3. Cut a piece of fiberglass cloth slightly larger than the damaged area.
  4. Mix polyester resin with hardener according to the manufacturer’s instructions, and apply it to the damaged area.
  5. Place the fiberglass cloth on top, ensuring it fully adheres to the resin. 
  6. Allow it to cure, and then sand the repaired area to blend it with the surrounding surface.
  7. Finally, apply a layer of gel coat and polish it for a seamless finish.
  8. Repairing Larger Damages and Holes:

For larger damages, such as holes in your fiberglass boat, the repair process requires additional steps.

Gather the following materials:

  • fiberglass fabric,
  • powdered fiberglass,
  • polyester resin,
  • elcoat, and
  • gel coat reducer.

Start by grinding away any damaged or delaminated fiberglass using a disc sander with a medium-grit sandpaper.

  1. Clean the area around the damaged section with acetone.
  2. Cut a piece of fiberglass fabric larger than the hole and saturate it with polyester resin. 
  3. Place the fiberglass fabric over the hole and apply more resin until the fabric is fully wetted out.
  4. Next, create a batch of gel coat by mixing the gelcoat with a gel coat reducer. 
  5. Apply the gel coat to the repaired area, and once it cures, sand and polishes it to achieve a smooth and glossy finish.

Step-by-Step Guide to Repairing a Fiberglass Boat

Step 1: Assess the Damage

Before starting any repair, assess the extent of the damage. Identify scratches, cracks, or holes that require attention. This evaluation will help you determine the appropriate repair technique and materials needed.

Step 2: Prepare the Repair Area

Clean the damaged area using acetone or a suitable cleaner to remove dirt, grease, and old wax. Ensure the area is dry and free of any contaminants before proceeding with the repair.

Step 3: Sand the Damaged Area

Use 80-grit sandpaper to roughen the damaged area and create a surface for the repair materials to adhere to. Sand until the damaged area is smooth and level with the surrounding surface.

Step 4: Apply the Repair Materials

For scratches and small holes, follow the process outlined in the previous section. For larger damages, use fiberglass fabric and polyester resin to create a strong and durable repair. Apply the repair materials according to the instructions provided, ensuring proper saturation and adhesion.

Step 5: Finish and Polish

Once the repair is done and the materials have cured, sand the repaired area using progressively finer grits of sandpaper, starting with 80-grit and finishing with 600-grit. This will help blend the repair with the surrounding surface. Finally, apply a coat of wax to protect the repaired area and restore the boat’s shine.

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Q: Can I repair a fiberglass boat hull from the outside on my own?

A: Yes, with the right materials and guidance, repairing a fiberglass boat hull from the outside is a task that boat owners can tackle themselves.

Q: How do I know if my fiberglass boat hull needs repairs?

A: Inspect your boat’s hull regularly for any visible damages such as scratches, cracks, or holes. Additionally, if you notice any signs of water leakage or structural issues, it’s essential to address them promptly.

Q: What are the basic materials needed for repairing a fiberglass boat?

A: The basic materials needed for fiberglass boat repair include gelcoat, fiberglass cloth, sandpaper, polyester resin, hardener, acetone, and clean rags.

Q: How do I repair scratches and small holes in a fiberglass boat?

A: To repair scratches and small holes, clean the damaged area, sand it to a smooth finish, apply a layer of polyester resin, place a fiberglass cloth patch, allow it to cure, and finish with a gelcoat layer.

Q: What should I do for larger damages and holes in my fiberglass boat?

A: For larger damages and holes, the repair process involves grinding away damaged fiberglass, cleaning the area, applying fiberglass fabric saturated with polyester resin, and finishing with a gelcoat layer.

Q: Can I use epoxy instead of polyester resin for fiberglass boat repairs?

A: Yes, epoxy resin can be used as an alternative to polyester resin for fiberglass boat repairs. However, it’s important to follow the manufacturer’s instructions and ensure compatibility with the existing materials.

Q: Are there any precautions to take during the repair process?

A: It’s crucial to work in a well-ventilated area and wear appropriate safety gear, including gloves and eye protection. Additionally, carefully follow the instructions provided with the repair materials and dispose of any waste properly.

Q: When should I consider seeking professional help for fiberglass boat repairs?

A: If you encounter extensive damages, structural issues, or feel unsure about your repair skills, it’s advisable to consult a professional boat repair service. They have the expertise and tools to handle complex repairs effectively.

Q: How long does it take for the repaired fiberglass to cure?

A: The curing time of fiberglass repairs depends on various factors such as temperature, humidity, and the specific materials used. Follow the manufacturer’s instructions for the recommended curing time.

Q: Can I use the boat immediately after completing the repairs?

A: It’s best to allow the repaired area to fully cure and harden before using the boat. Refer to the specific curing time provided with the materials and avoid exposing the repaired area to stress or water until it’s completely cured.


Repairing a fiberglass hull from the outside is a manageable task that any boat owner can accomplish with the right tools, materials, and guidance. By following the step-by-step guide provided in this article, you can effectively repair scratches, small holes, and even larger damages, ensuring your fiberglass boat remains in top condition. Remember, proper repair techniques and attention to detail are key to maintaining the structural integrity and longevity of your boat. So, equip yourself with the necessary knowledge and embark on your next fiberglass boat repair project with confidence.


  • Anna Kristensen

    Anna Kristensen is an avid sailor and experienced yacht captain. With her vast experience sailing across different seas and weather conditions, she offers expert advice on navigation, seamanship, and offshore sailing. Anna's in-depth knowledge of sailing techniques, safety protocols, and voyage planning makes her an excellent resource for sailors looking to enhance their skills and embark on memorable boating adventures.

    Kristensen Anna

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