Most boat owners don’t consider the maintenance of their vessel when making your purchase. You’re so wrapped up in the excitement of getting out on the water that the thought of maintenance and repairs is the last thing on your mind.
However, there comes a day in every boat owner’s life when they notice a scratch or ding in the hull. The hull has a “gel coat” covering that’s weather-resistant, ensuring that the materials used in the hull construction don’t experience any seawater damage.
The gel coat also provides the look of the boat. Take a look at a boat in a dealership with a freshly polished gel coat, and you’ll notice it has a beautiful, smooth finish. When the gel coat cracks, it allows water to seep into the fiberglass or wood frame and materials like the coring.
As a result, you end up with a damaged boat that requires immediate repairs. Fortunately, repairing the gel coat yourself isn’t as challenging as you think., This guide gives you everything you need to know about how to repair gel coat surfaces on your boat.
Contents
What Is Gelcoat?
The gel coat is a polyester resin-based thermoset polymer or epoxy resin applied to the hull exterior in the fiberglass molding process. The gel coat gives the boat a smooth, shiny, clean look when it rolls onto the showroom floor.
However, the gel coat does more than provide a glossy, attractive finish to the boat. It’s a waterproofing barrier that protects the coring and fiberglass materials underneath. The gel coat prevents hydrolysis and UV damage to these construction materials, ensuring a longer service life for the vessel.
After application, the gel coat shrinks to 4% to 7% of its original surface area, with less than 1% elongation in the cure. As a result, the gel coat gets a rock-hard cure, but it also means that the gel coat is brittle, especially when applied too thick.
Gel coat applications should be approximately 20-mm (.020 of an inch) thick when applied properly by the manufacturer. However, when the boat builder sprays the gel coat on the fiberglass mold of the boat deck featuring seatbacks and cabin top corners, the edges seem to get more gel coat than they need.
Or the gel coat can run down the interior and build up in the corner. Or the manufacturer will spray too little or too much gel coat on the entire mold. Fiberglass weakens after prolonged exposure to water, so your gel coat needs to be in immaculate condition at all times.
However, the film can degrade over time despite the gel coat’s durability. High-performance boats like consoles and bay boats experience flexion in the frame as they move through the water at speed. Over time, this flexion can weaken specific areas of the gel coat, resulting in cracks.
When you notice cracks, you need to repair them immediately.
What are the Types of Gelcoat Damage?
There are different types of cracks, and they occur for various reasons. Here are the common types of cracks you’ll find in your boat’s gel coat.
- Minor Single-Line Cracks
The thicker areas of the gel coat don’t have the reinforcing fabric to hold everything together. As a result, it relieves the stress in the form of a crack. This occurs when pulling the part from the mold or flexing stress years down the road. - Screw Hole Cracks
Hairline cracks originating from deck hardware. These cracks occur after installing hardware on the boat. The screw heads create pressure that causes cracking. You’ll often find them around snaps for beverage and canvas holders. - Stress Cracks
A concentration of cracks running in the same direction indicates a severe structural problem. These cracks can occur in a high-flex area enduring too much load or heavy seas. Cracks typically form at a bulkhead or in hard spots behind fiberglass. - Thermal Fatigue Cracks
Short, random cracks are also known as “crazing.” The heat change in the local environment can break down the gel coat over time, causing expansion and contraction with the temperature change that leads to cracking. - Spider Cracks
An indication of structural damage may also result from inflexible gel coats applied too thick.
A Step-By-Step Process to Repairing Your Boats Gelcoat
It seems like every boat owner has a method for fixing gel coat cracks. However, we decided to give you this proven method to repair your boat. There are several strategies for repairing gel coats, depending on the severity of the damage in the affected area.
If the gel coat oxidizes over time, it will have a chalky, dull appearance. You can bring it back to its former luster using gel coat oxidation remover and a buffing machine to polish the gel coat back to a high sheen and gloss.
In some cases, you might have to use a polishing compound to remove some of the old haze on the gel coat and restore its former glory. Regardless of the problem, here is our guide to repairing your gel coat.
Step 1 – Identify Your Boats Finish
It’s important to note that the gel coat won’t bond to a painted hull. Therefore, you’ll need to identify the finish before settling on the right gel coat for the repair.
Boats with fiberglass, polyester resin, resin, or gel coat finish don’t require additional repair steps before finishing. However, painted vessels need you to remove the paint before applying the fresh gel coat.
Step 2 – Prepare the Surface
The final gel coat layer has a waxy component to it. Therefore, you’ll need to remove this waxy finish from an area twice the diameter of the damage in the affected area.
If you’re making deeper gouge repair, you’ll need a power drill and a conical grinding stone with a V-taper to remove material around the area, smooth it out, and improve the bonding of the gel coat to the affected area.
Use 80-grit sandpaper wrapped around a sanding block and remove any loose chips. Create a shallow bevel on the edges of the repair area and clean it up with acetone before applying the gel coat.
Step 3 – Tape off the Work Area
You can use painter tape to tape off a 1/16th-inch perimeter on the gel coat around the damaged area. Tape off adjacent or sensitive areas that may experience accidental contact with sandpaper or gel coat spatter.
You can also use masking paper if you’re spraying the gel coat on. Sand the taped area with 360-grit sandpaper to get the gel coat to stick, and wipe the sanded area down with acetone.
Step 4 – Mix and Apply the Filler
If you’re dealing with a deep gouge, you’ll need to fill it with epoxy before applying the gel coat. Epoxy is more expensive than the traditional polyester filler, but it sticks better, providing a better bond over the years for a better repair job than polyester filler.
However, you’ll have to complete some additional preparations before applying your final gel coat. After you finish filling the area and the poxy cures to full hardness, it’s time to start sanding to perfection and wipe down the area with acetone when you finish.
Step 5 – Complete the Color Match
Make sure the gel coat provider matches the tint of the new gel coat to your boat. If you buy a new boat, ask the dealer to provide you with a sample of the gel coat for future repair jobs.
Alternatively, check online for gel coat repair kits that feature pigments you can add to the resin. Always match the pigments in the bright sunlight, not the shade.
Step 6 – Mix Your Paint and Catalyst
After you have the color of the gel coat matched, it’s time to add your catalyst to the base in the correct ratio. Too little or much catalyst prevents proper curing of the gel coat.
Most manufacturers use a 2:1 ratio, but check the instructions before adding the catalyst. Check the viscosity of the gel coat when considering the application method.
Spray applications give you the most consistent and accurate coating, especially on vertical surfaces that might experience dripping. Use a styrene thinner to thin your base for spraying.
Step 7 – Apply Your Gelcoat
If you’re using a spray gun for application, attach the hose to the compressor and fill the can reservoir with the gel coat.
Apply the base coat of gel coat with short strokes moving away from the repaired area. Lt the gel coat gas off for 20-minutes before adding a second coat. It might take around five to six coats to get to a 20-mm thickness.
If you’re using a brush application, we recommend a foam roller to prevent streaks, drips, and brushstrokes. Apply your gel coat in vertical, short strokes. Build the film higher than the surrounding area to compensate for sanding.
After your final coat dries, coat it with a PVA curing agent and wait for 48-hours for it to cure fully.
Step 8 – Sanding, Buffing, and Polishing
After the PVA reaches full cure, sand it with 320-grit wet/dry sandpaper wrapped around a sanding block. Next, change to a 600-grit and continue with your wet sanding of the immediate repair site and surrounding area.
Finish the repair with 1,000-grit water paper and buff the repair area with a polishing compound. After buffing, apply a coat of wax polish and buff it out to a shine.
How Do I Repair Minor Gelcoat Cracks?
To repair minor cracks in the gel coat:
- Start with a rotary tool to open the crack to a “V” shape.
- Fold a sheet of 80-grit sandpaper to make it rigid and scuff the open area.
- Remove the dust and fill the crack with epoxy resin supported with silica adhesive filler.
After the epoxy cures:
- Wash the repaired area with water to remove amine blush.
- Sand the area and apply your gel coat to the repaired area.
- Add fiberglass reinforcement to the backside if the gel coat cracks occur due to fiberglass flexing future cracks.
Seal screw hole repairs with epoxy if a fiberglass core is behind it. With a foam or balsa core, take a bent nail, remove some of the core., Fill the area with high-density adhesive filler.
If you’re repairing plywood or other wood cores, drill an oversized hole and fill it with high-density adhesive filler. These methods create a good seal with the core and more molding strength for your fasteners.
How to Repair Gelcoat FAQs
Q: How do I repair a gouge in a fiberglass boat?
A: Fill the gouge with filler and sand out any other scratches while waiting for the filler to cure. Apply your gel coat to the filled gouges and scratches and finish with sanding the filled gouges. Ensure you buff out all the repaired areas to get a seamless look to the finish.
Q: When do I need to repair cracks in the gel coat?
A: You’ll need to repair the gel coat as soon as you notice any cracks or scratches. Immediate repair ensures you don’t have to deal with water damage to the fiberglass structure of the boat. Water damage will soften and destroy fiberglass and rust the hardware components in the affected area of the boat.
Q: What does professional gel coat repair cost?
A: Repairing the gel coat yourself is a great way to save some money you can use for bait or gas for your next fishing trip. However, we understand that some boaters just don’t have the time to spend with a DIY gel coat repair. If you’re looking to get a professional to repair the crack, you could pay anywhere from $70 to $100 per hour for the labor, excluding the gel coat and sundries required for the job.
Q: Can I blend my gel coat?
A: Yes, you can wet sand the repair work to seamlessly blend the new gel coat into the original. Start with 240-grit sandpaper followed by 400-grit and finish with 600-grit sandpaper. To stop ridging, wrap a block of wood around the paper.
Q: What is a brushable gel coat?
A: The brushable gel coat offers boaters a purpose-formulated product designed to apply like paint and do away with the need for spray equipment during the repair process. You get excellent leveling with a brushable gel coat, good water and osmosis resistance, UV light stability, durability, and great gloss retention.
