How to Repair a Damaged Fiberglass Boat Floor

  • 2-6 hours
  • Beginner
  • 75-150
What You'll Need
Fiberglass boat repair kit
Warm water
Disk sander
Wax paste
Plastic putty knife
Razor knife
Fiberglass cloth
Fiberglass mats
PVA mould release

A fiberglass boat floor is one of the best choices you can make for your boat. Fiberglass has an extremely high resistance to water because of its non-porous quality. This makes it a highly suitable material for boat construction. However, your boat may suffer some impact during use, which may result in damages to the floor. Fortunately, it isn't complicated to repair a fiberglass boat. Follow the simple steps below to complete this project.

Step 1 – Assess the Damage

To begin, take the time to evaluate the extent of the damaged area. Use a saw to cut away the damaged portion of the floor. It is best to cut out the material in a circular shape. This makes it easier to patch later. Be sure to cut at least a ½-inch beyond the damaged portion to ensure that you completely extract the damaged fiberglass.

Step 2 – De-Wax

Fiberglass boats are usually waxed, and you must remove the wax before you can repair. Wash the area with a solvent to get rid of the wax. This will facilitate repair and guard the fiberglass from cracks which tend to weaken the floor further. Wipe the area with a rag.

Step 3 – Sand

Bevel around the hole with a 36-grit disc. You should get a uniformly dull look. Wipe along the circumference of the hole and adjacent areas with acetone and a clean rag.

Step 4 – Apply Resin

Use a plastic putty knife to apply a thick coat of resin around the area.

Step 5 – Attach Formica

You need some form of “backing” in the hole as you install the replacement fiberglass. Place a piece of formica that is large enough to cover the hole from inside the hull. This will allow you to work from the outside.

Step 6 – Cut Out Fiberglass Patches

Cut a piece of glass cloth that covers the hole adequately. It should exceed the hole by 1 inch all round. Next, cut out another cloth that exceeds the previous by a ½-nch. Cut out a piece of fiberglass mat that exceeds the cloth by a ½-inch around the circumference. Follow this with 3 to 4 mats. Each successive layer of material you cut out should exceed the previous layer by a ½-inch around the circumference.

Step 7 – Attach Fiberglass Cloth and Mats

Mix some resin and catalyst from your fiberglass kit. Attach the smallest piece of glass cloth onto the hole. Spread some resin on the surface and attach another glass cloth. Spread resin on the cloth then spread the smallest fiberglass mat over the cloth. Use an air roller over the patch to get rid of air bubbles.

Apply resin and attach the next bigger sized mat onto the cloth. Spread some more resin. Continue to work this way until the fiberglass is flush with the floor. Cut off the excess material and layer onto the patch. Seal the patch with PVA mould release.

Step 8 – Finish Up

Remove the formica from inside the hull. Fill gaps with resin, and apply a gel coat that matches the floor.