Hull, gelcoat & antifouling

How to repair boat gelcoat: chips, scratches and cracks

Updated: 5 min readCaranva Boats

Quick answer

To repair a gelcoat chip, clean and degrease the area, open the damage into a V, fill with gelcoat tinted to the hull colour (with catalyst), cover it so it cures without air, wet-sand through progressive grits and polish to match the gloss. Damage reaching the fibreglass or core needs new laminate.

Steps

  1. Clean and degrease the area with acetone.
  2. Open the chip or crack into a V with a burr or sandpaper.
  3. Tint the gelcoat to match and add catalyst.
  4. Overfill slightly and cover with film so it cures without air.
  5. Wet-sand through progressive grits (320 to 2000).
  6. Polish with compound and finishing polish, then wax.

DIY or professional?

Small scratches and chips above the waterline can be repaired with a gelcoat kit and patience. Call a professional if:

  • The damage exposes fibreglass or the cloth is broken.
  • It sounds hollow when tapped around it (possible delamination).
  • It is below the waterline or near structural fittings.
  • You suspect osmosis (blisters below the waterline).

Materials

Gelcoat or gelcoat paste, catalyst, colour pigments, acetone, PVA or plastic film, wet-and-dry paper from 320 to 2000, polishing compound and wax.

Step by step

  1. Clean and degrease with acetone.
  2. Open the damage into a V so the filler bonds well.
  3. Match the colour by tinting small test batches; remember the hull may have yellowed.
  4. Catalyse and fill, leaving a little excess.
  5. Cover with film or PVA: gelcoat doesn’t cure properly in contact with air.
  6. Wet-sand up through the grits until flush.
  7. Polish with compound and finishing polish, then wax. See how to polish and wax a boat.

Stress cracks

Fine spider-web cracks usually point to stress or flexing. If they appear around stanchions or cleats, check the mounting before filling or they will return.

If you’d rather leave it to the experts, see our gelcoat repair service or find paint and gelcoat professionals.

Frequently asked questions

How long does gelcoat take to cure?

It depends on catalyst and temperature: usually a few hours before sanding. Cold or humid conditions slow it down and worsen the finish.

Will the repair be visible?

If the colour is well matched and properly polished, it is barely noticeable. On heavily yellowed hulls it’s harder and polishing the whole area may be best.

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