How to repair gelcoat on bottom of a boat? Some information about gelcoat

Do you want to know how to repair gelcoat on the bottom of a boat? Whether you need to repair a single spot or refinish an entire area, tackling repairs yourself can save time and money in the long run.

How to repair gelcoat on bottom of a boat? Some information about gelcoat

How to repair gelcoat on bottom of a boat? Some information about gelcoat

In this blog post, Scott Ewart discusses how to repair the gelcoat on a boat with step-by-step instructions. Furthermore, we will assist you in thoroughly comprehending some information about gelcoat. Let’s get started so that later you can do anything by yourself without worrying!

How to repair gelcoat on bottom of boat

It can be hard and take a lot of time to fix the gelcoat on the bottom of a boat. The important thing is that repairing gelcoat requires proper preparation, materials, and techniques. Here are steps to help you do it easily:

Step 1: Prepare the tools and equipment

Step 1: Prepare the tools and equipment

Step 1: Prepare the tools and equipment

Here are the needed tools:

  • Protective eyewear
  • Respirator Mask
  • Fine-grit Sandpaper
  • Wax Remover
  • Gelcoat Scrub Pad or Brush
  • Gelcoat Filler and/or Repair Compound
  • Putty Knife or Spreader

Step 2: Determine the boat’s previous gel polish finish

Before fixing a boat, you have to make sure what kind of finish it has because gelcoat can’t stick to painted surfaces. Gelcoat, fiberglass, and polyester resin-based boats don’t require any additional preparation before repair. However, prior to applying gelcoat to painted vessels, they must be stripped of existing paint first.

Step 3: Clean the surface of the boat bottom

Step 3: Clean the surface of the boat bottom.

Step 3: Clean the surface of the boat bottom.

The important reminder: You should wear safety glasses, gloves, and a face mask to protect your eyes and skin.

  1. Utilizing a rotary tool and burr bit, refine taper gouges for the perfect shape.
  2. Attach a V-shaped burr bit to your Dremel tool, then switch it on and press the end of the bit against the gouge at an angle of 45 degrees.
  3. Gently buff the jagged edge of the gouge to achieve a smoother surface.
  4. Form a U-shaped ditch by repeating the process on the opposite side.

Step 4: Sand out small scratches and gouges

Attach a piece of sandpaper with 80 grit to your sander and move the machine in a circular motion around the repair area. Using different sandpaper until they are completely removed.
Steps Some kind of sandpaper



80-grit sandpaper Sand the scrape until it is flush with the surrounding area.


150-grit sandpaper

Sand the scarred area until it is equally smooth

3 240-grit sandpaper

Sand the surface until the texture is even smoother and the damage is concealed by the surrounding material.

Step 5: Wipe down the area using acetone

Be sure to use a cloth or sponge soaked in acetone and wring it out before wiping down the area.

This will prepare the surface for epoxy filler application.

Step 6: Tape off the area you are repairing

Step 6: Tape off the area you are repairing.

Step 6: Tape off the area you are repairing.

  1. Adhere masking tape around the edges of the gel coat repair area so that it won’t get sanded away.
  2. Create a 1/16-inch perimeter around the damaged spots with painter’s tape.
  3. Tape off any areas that might get damaged by gelcoat splatters or accidental sanding.
  4. Masking paper can prevent overspray from gelcoat restorer sprays.
  5. Sand the whole taped-off area with 360-grit paper and clean with acetone.

Step 7: Apply a coat of filler over the repaired area

Apply a coat of epoxy filler over the repaired area

Apply a coat of epoxy filler over the repaired area

With the deep scratches or gouges, you have to fill them in with an epoxy filler. The best product for this is a two-part epoxy like West System or System Three.
  1. Mix the appropriate amounts of resin and hardener as per the manufacturer’s directions.
  2. Then carefully spread it on the repair area using a putty knife or plastic scraper.
  3. When your area is filled and dried, give it a sanding treatment afterwards
  4. Then wipe off the dust with acetone for a cleaner finish.

Step 8: Purchase a gel coat that is compatible with the old gel coat

how to re gelcoat a boat

how to re gelcoat a boat

A gelcoat repair kit is a two-part solution that needs to be mixed quickly and correctly before it can be applied to the damaged area.

To achieve the desired color for a project, you have two options. You can take extra time to find the exact shade. Or you can invest in materials that come with an array of hues, allowing you to customize your mixture as needed.

Step 9: Mix the gel coat with the catalyst

Following the manufacturer’s instructions to mix the gel coat, you will need to measure out and mix in a catalyst. This is usually a two-part mixture of polyester resin and MEKP (methyl ethyl ketone peroxide). The ratio of the two components will vary from manufacturer to manufacturer.

The catalyst solution is either sprayed together with the resin or gelcoat during spray lay-up (Mechanical)


Step 10: Apply the mixture to the boat’s damaged areas

Step 10: Apply the mixture to the boat's damaged areas 

Step 10: Apply the mixture to the boat’s damaged areas

Case 1: Use the spray applicator

  1. Pour the repair gelcoat into the applicator bottle.
  2. Fill the container with gelcoat if you will be applying it with a spray bottle, then connect the hose to the air compressor.
  3. Pump the handle of the applicator until repair gelcoat comes out of the nozzle in an even stream.
  4. Apply a thin layer of gel polish with small strokes, starting from the damaged area and moving outward.
  5. Give the solvent about 20 minutes to evaporate between each coat.
  6. You’ll probably need five or six coats before you get a 15- to 20-mm-thick coat.

Case 2: Use a foam brush or roller to apply gelcoat

  1. Use either a foam brush or painting roller to apply the new gelcoat.
  2. It is recommended to use short, vertical strokes when applying the gel coat.
  3. To allow room for sanding, build a film just slightly above the area surrounding the damaged area.
  4. Once the final coat has had time to dry, apply a PVA curing agent to the area and wait for the cure to dry completely before continuing.
  5. To ensure the gelcoat fully sets, allow it to dry for at least 8 hours before use.

A paint roller comprising a frame having a handle portion and a shaft, a sleeve support rotatably mounted on the shaft for receiving a roller sleeve


Step 11: Sand down the damaged area on the boat’s bottom

Sand down the area where you made repairs to the gelcoat using wet or dry sandpaper and progressively finer grits of paper until it is smooth. For each stage of sanding on the repaired spot on bottom of a boat, we use different sandpaper:


Types of sand paper Usage


80-grit sandpaper

Sand down until the area that was restored is at the same level as the area around it.


400-grit paper

Sand it until there are no rough spots left.

3 1,000-grit paper

Apply rubbing compound to the area and polish it.

Step 12: Polish the repaired area

Step 12: Polish the repaired area

Step 12: Polish the repaired area

For a smooth polish, carefully apply the rubbing compound to your electric buffer pad and turn it on at low speed. If you want the best results, stop buffing as soon as the paste has dried. Gently buff the mended area before using tape to finish.

As you move along, wipe away any remaining residue from the rubbing compound using a fresh cloth.

Step 13: Wax the repaired spot on the bottom of the boat

Once you have finished buffing the repaired area, it is time to wax it. To do this, get a good-quality marine wax and evenly apply it over the entire bottom of your boat with a clean cloth or applicator pad.

Allow the wax to dry for 10 to 15 minutes before wiping away any excess product with a soft cloth. Make sure to wax the entire bottom of your boat; this will help protect it from the elements and give it a glossy finish.

That’s 13 simple and detailed steps to help you know how to repair gel coat on a boat. If you want to only restore gelcoat at any areas, you can consult how to restore gelcoat on a boat here. You can follow along and complete your process successfully!

Some information about gelcoat

Some information about gelcoat

Some information about gelcoat

Gelcoat is a type of coating used to protect and beautify the surfaces of boats, cars, and other items. It is typically made up of a polyester resin that has been catalyzed with a hardener and then pigmented with various colors.
Gelcoat is applied as a thick liquid and cures quickly, forming a hard, protective surface. To know more about gelcoat, you can read what to know about a gel coat here.

FAQs How to repair gelcoat on bottom of boat

Can gelcoat be restored?

Yes, it is possible to restore gelcoat. Gelcoat, despite being a soft surface, eventually becomes dull and chalky due to wear and tear or sun exposure. Fortunately, its original shine can usually be restored.

Does gelcoat adhere to gelcoat?

Only fiberglass, gelcoat that has already dried, or polyester resin will hold gelcoat in place. Gelcoat won’t attach to paint or protective coatings, so avoid applying it to them. It will be necessary to remove the old paint.

Is reapplying gel coat on a boat possible?

To keep your boat safe and working well, you need to replace the protective gelcoat on it every so often. This clear or colored resin should be refreshed every few years for the best results.

Does gelcoat require sanding in between coats?

If you haven’t used a surfacing agent (8140 or 8185) on your gel coat, sanding between applications is not necessary. To avoid a cluster of gel coat, create a “flow” or sanding layer on the covered area after your repair is complete. This will help you maintain an even appearance and prevent any build-up from occurring.


Now that you have a better understanding of how to repair gelcoat on the bottom of a boat, it is time to take action. All of the necessary supplies can be easily acquired with the help of a boat supply store, and a few hours should be enough for the repair process. Don’t forget to pay close attention to any painting instructions and details while working on this project. If you have any questions, don’t hesitate to leave a comment below. We are from and are willing to help you!

Leave a Reply