The fiberglass of a boat can get pinholes when a small blister forms in the gel coat layer. Over time, water will erodes the blistered border and open up a pinhole. The problem with pinholes is the future damage they can cause. As water enters this tiny opening, it will spread and eventually lead to cracks or flexing damage. What was once a hole you could barely see is now a substantial repair job. Fixing a pinhole in your fiberglass boat is straightforward and takes little time, but can help you avoid large problems later.
Step 1
Examine the pinhole and the surrounding area for other damage. A pinhole can exist by itself, but there may be other damage in the area, such as blistering or scratches. Inspect the area thoroughly on the inside and outside. Look for cracking on the inside, as this would indicate flexing and require more extensive repair.
Step 2
Wipe the area around the pinhole with acetone applied to a cloth. This will clean the area and take off wax. Dry the spot with a paper towel.
Step 3
Sand the pinhole with a 150- to 200-grit sand block if there is beveling or a raised surface. Sand enough so the hole is level with the hull.
Step 4
Apply a gel coat filler or putty to the hole with a mixing stick or scraper. Remove excess compound with a scraper or cloth. Fill just past the surface of the hull so the area extends past the flat area. Let the compound cure completely following the instructions provided with the product.
Step 5
Sand down the filler so it is flush with the hull surface. Then wet-sand the area with 220-grit sanding to finish it. Wet sanding is done with a sanding block designed for the purpose. Wet the block or the surface, and sand normally.
Tips and Warnings
- For on-the-water repair of pinholes, keep a roll of duct tape handy. Duct tape will cover the hole until you get to land and can fill it.
Things You'll Need
- Acetone
- Clean cloth
- 150 to 200 grit sandblock
- Gel coat filler or putty fill
- Mixing stick
- Paint scraper
- 220-grit wet sanding block
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