The next time you're cleaning and waxing your boat, take the time to look for small cracks, scratches and chips in its gel coat. If your boat is more than a few years old, you'll probably be surprised at the number you find. We'll guide you through the process of repairing them.
Skill Level Description (10=most difficult, 1=easiest)
- Buffing out an oxidized boat: 2
- Wet sanding scratches, then buffing: 4
- Filling gelcoat scratches on a white boat: 4
- Filling gelcoat on a colored boat: 6
Tools and Materials You Need to Repair Gelcoat
- Sanding Block
- Wet/dry sandpaper sheets, from 220 to 600 grit
- Right Angle Power Buffer
- Bucket, water, boat soap
- Goggles
- Gelcoat
- Rubbing Compound, Finishing Compound, Wax or One-Part Cleaner Wax
- Sandpaper
- Resin Tools
- Application Brushes
- Plastic Spreaders
- Epoxy Syringes
- Reusable Mixing Sticks
Diagnosing Gelcoat Damage
Most scratches and chips in gelcoat result from impacts with hard objects (winch handles, downrigger weights, 15-pound lobsters) and are not cause for concern. But if you find a series of cracks, take a minute to inspect the area more closely. If the cracks radiate from the base of load-bearing equipment like a cleat or stanchion, there is probably a problem with the installation that deserves attention before repairing the gelcoat. Solving it might be as simple as shifting a load from undersized equipment, or installing a larger backing plate to spread the load over a wider area. If cracks appear at important joints or intersections in the cabin or deck, however, they might be the sign of an underlying structural weakness that needs to be examined. You might consider hiring a marine surveyor or having a qualified boat maintenance worker take a look at the problem to ensure that it isn't serious.
Step-by-Step Guide to Repairing Minor Gelcoat Damage
A gelcoat repair kit like this one has everything you need for color matching and making minor repairs to dings and chips in your gelcoat.
Step 1: Wash the repair area with soap and water, rinse it thoroughly, and allow it to dry completely. If the surface is oxidized, restore it with a rubbing compound; this is important because you’ll want the original surface color visible to accurately match your gelcoat paste. Once the surface is clean and dry, mark off the repair area with masking tape.
Step 2: Gouge out small, narrow cracks—along with any scratches too deep to remove with rubbing compound—until they are wide enough to accept gelcoat paste. A miniature grinding tool like a Dremel works best, but the sharp point of a can opener can be used in a pinch. If you don’t open up the crack, you won’t be able to force gelcoat into the repair area or expose enough surface to ensure proper adhesion. After shaping the crack, sand the area lightly using 220-grit sandpaper.
Step 3: Thoroughly clean the sanded area with acetone to remove sanding residue, waxes, and any other contaminants that could interfere with the bond between the existing surface and the new gelcoat. Provide adequate ventilation and wear appropriate protection for your skin and eyes whenever you work with acetone.
Step 4: Match the color of the existing gelcoat. Start with a white or neutral gelcoat paste (not resin) and add tiny amounts of coloring agent. Mix several small test batches with pigment, add hardener, and allow each batch to cure—gelcoat changes color during the curing process. Once you’ve found a satisfactory match (an exact match is nearly impossible), mix your final batch using the same pigment-to-paste ratio.
Step 5: Using a putty knife, apply the mixed gelcoat paste to the cracks or damaged areas. Be sure to force out any air holes and overfill slightly, as gelcoat tends to shrink while curing. When finished, seal the repair from exposure to air using a PVA curing agent, or by covering the area with plastic wrap or wax paper. Gelcoat does not cure properly when exposed to air.
Step 6: After the gelcoat has fully cured, sand the repaired area smooth. Wet sanding is especially effective with gelcoat. Begin with 220-grit sandpaper and progress to at least 400- or 600-grit for a slick, near-factory surface.
Step 7: Apply a coat of high-quality marine polish to restore shine and blend the repaired area with the surrounding surface—your gelcoat repair is now complete.