One of the best qualities of a fiberglass boat is how easy it is to repair. While a damaged wood boat requires expensive and intricate work, a fiberglass one can usually be repaired with just a few materials, even by people with only basic knowledge and skills. Another great quality of a fiberglass boat is that, once repaired, it looks as good as new. After the new layer of fiberglass dries, it becomes part of the boat, rather than a superficial patch.
To repair a fiberglass boat, start by cutting away the damaged area. To make sure you're stripping away all the damage, always remove an area at least half an inch (1.27 cm) larger than the damage you see at first view. This type of boat is always waxed, so before you attempt to repair the hole, wash the area with a solvent. Getting rid of the wax will not only make the process easier, but it will also prevent the inner surface of the boat from cracking and weakening. Next, using a disk sander, grind the area surrounding the hole until you get a distinct, uniformly dull look on the surface, and then apply a heavy coat of paste wax.
There are several materials you can use to repair a fiberglass boat, but for the inexperienced boat owner, it is best to buy a repair kit. Start by taping a piece of Formica or Plexiglas to the inner surface of the boat, making sure to cover the hole thoroughly. This will serve as backing. Next, mix all the materials that come in the kit – usually some type of resin and a hardening agent. Fill in the damaged spot until it's level with the hull of the boat, and then smooth the area with release paper or cellophane for a high-gloss finish.
If your fiberglass boat only has superficial damage, such as scratches and cracks, sand the area and remove the wax with a solvent before applying a store-bought plastic filler such as Gelcote. Wait for the plastic filler to cure before applying another coat. Two coats are usually enough to repair standard damage in the typical fiberglass boat. Finish by sanding the filler to a smooth level and follow with a coat of primer.