How to Repair Gel-coat

The damaged gunwale.

The damaged gunwale.

Got a few dings this summer? Here are some gel-coat repair tips.

Fibreglass is made from tiny glass strands, either woven into a mat, or randomly oriented by chop-gun application. It has thousands of uses – hot tubs, shower stalls, cars and boats to name a few. Boats are usually made in female moulds. The mould is first coated with a release agent (a heavy wax for example). Next a two-part gel coat is sprayed in the mould. Once it dries the fibreglass mats are hand-laid into the mould, and soaked with a polyester or epoxy resin. When everything dries, the components are popped out of the mould, exposing a perfect gel-coat finish.

It is this gel-coat finish that takes most of the abuse when it comes to the inevitable nicks and scratches. Gel-coat differs from paint in both its strength and its thickness. Since it is much thicker than paint, most light scratches can be buffed out completely with a heavy rubbing compound. Deeper scratches that don’t penetrate through gel coat can be lightly wet-sanded with 400 grit wet/dry sandpaper to smooth the area, then progressively with finer and finer sandpaper, for example 1000, 1500, and finally 2000 before using a rubbing compound to restore the shine.

Scratches that are deeper still may require a gel-coat repair product. I’ve used two products before, both marketed by Evercoat. For small scratches in white gel-coat, a one-step product called No Run Gel-coat Paste is available. Since it is not catalyzed it should only be used in small doses. Once dry it can be lightly buffed as mentioned above. The second product is more expensive, the Match’n’ Patch. This comes supplied as a kit, with a two-part (catalyzed) gel-coat and a variety of pigments that allow you to match any colour.

I’ve used this second product to repair some serious damage on a jet boat, and a deep, long scratch on a fibreglass car body. As you can see from the images, by following the instructions you can clean, prepare, mix, and apply the repair. Once applied, the kit comes with a clear release film that is placed over the repair to get a perfectly smooth finish. I found this step a little tedious and preferred to build up the material thicker than needed so I could sand and buff the area to a perfect finish. Try it both ways and see which you prefer.

Consider giving your boat a once-over in the spring or fall. With the right products and some practice, you can get it looking as good as new.

For more boat maintenance information register for the CPS-ECP Boat and Engine Maintenance Course at:

By: Bradley Schmidt

The No-Run Paste and the contents of the Match'n' Patch Kit.

The No-Run Paste and the contents of the Match’n’ Patch Kit.

The two-part mixture ready for use.

The two-part mixture ready for use.

The mixture applied to the gunwale with the release film on top.

The mixture applied to the gunwale with the release film on top.

4 thoughts on “How to Repair Gel-coat

  1. Putting off boat repairs is never a good idea. Especially if you keep taking your boat out on the water with the damages. I’ll have to try this mixture next time my boat gets a ding. Last summer I saw about 15 boats get pretty damaged from a wild storm while they were docked. It’s always unfortunate, especially for the more expensive boats! Thanks for the article!

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