Minor gelcoat repairs

Oops! You scratched the gelcoat on your boat. It’s actually easy to repair, but if a boatyard makes the repair, it can be expensive. Doing it yourself is not difficult if you take it step-by-step. Here are the steps to a clean repair:

1. First remove any loose material. Often gelcoat around the damaged area is cracked and should be removed. If you have a small area of damage, use a Dremel tool with a V-shaped grinding bit. If you have a large area to repair use a grinder.

2. When the area is free of loose material, wipe it down with solvent to remove any grease or oil.

3. If you are not sure of your ability to make a mess, mask off the area with masking tape and plastic, leaving only the damaged area showing.

4. Mix the first batch of gelcoat. Stir it well. You don’t need a lot of gelcoat mixture. You can always more gelcoat, but removing too much mixture after it has dried can be a lot of hard work. If the existing gelcoat is colored add a drop of coloring agent and see how well it matches. Adjust the coloring agent until you have approximately the right color.

5. Wipe the job with solvent to ensure it is still clean and oil free.

6. Apply the new gelcoat. I prefer to use a disposable Craft stick as a stirrer and as a spatula for tiny jobs. If you have to cover a larger area use a flexible plastic spatula. If the hole is deep, apply the gelcoat in layers until you have built up the gelcoat layer. This also gives you the chance to adjust the colors. You’ll find that the new mixture is slightly darker when wet than dry.

7. Wait until the gelcoat has dried and hardened, at least 24 hours, then sand with fine sandpaper. You will probably need to add another layer of gelcoat.

8. When the gelcoat is dry, sand with at least 400-grit sandpaper, 600-grit is better. For a final layer, touch up the job with a brush.

9. With the job’s done, sand it with 600-grit and burnish with rubbing compound until the repair matches the nearby area.

If you have a large shallow area to cover, you may want to brush the gelcoat on in layers until you have built up the right thickness. Gelcoat is only 10 to 20 microns thick, so you won’t need a lot of material to repair it.

If the damage has gone through into the underlying fiberglass laminate, your problem is slightly larger and you will need to grind the damaged area back before adding additional layers of fiberglass.

Roger Marshall’s latest book is Fiberglass Boat Repairs Illustrated.


Use rubber gloves to protect your hands when using fiberglass or solvents.
Use safety glass if you plan on grinding.
Use a dust mask or respirator if you do any grinding of fiberglass or gelcoat.
Do not breathe the solvent fumes.

By Ocean Navigator