How to Repair Rotted Wood in a Fiberglass Boat

Rotted wood can be a major problem in boats, whether made of fiberglass or not. If the rot is not repaired, it can eventually cause the boat to sink. This post will show you how to repair rotted wood in a fiberglass boat using epoxy putty.

How to Repair Rotted Wood in a Fiberglass Boat

Epoxy putty is a great choice for repairing rotted wood because it is durable and waterproof. Read on for instructions on using epoxy putty to fix your boat’s rot issue. We will also discuss some prevention tips to help you avoid this problem in the future. Let’s get started!

Summary: If your fiberglass boat has rotted wood, there are a few simple steps you can take to repair the damage. First, remove any loose pieces of wood with a screwdriver. Next, use a saw to cut out the rotted area. Finally, use a filler and sealer to fill in the hole and protect the wood from future decay.

10 Effective Ways on How to Repair Rotted Wood in a Fiberglass Boat

1. Remove All Loose Rotted Wood:

If there is rot on a piece of wood, use a saw to cut around the edges of the rotted area. Then, use a putty knife to scrape away any remaining decayed material and tiny fiberglass pieces from inside the hole. Vacuum the area to remove all dust and particles, then wash it thoroughly with acetone or alcohol. Allow the area to dry completely, then fill the hole with epoxy using a caulk gun.

2. Cut Out Section of Fiberglass Sheeting:

Cut out the section of fiberglass sheeting that is larger than the rotted area. Cut a new piece to fit and place it over the rotted wood, overlapping the old piece by 1/4-inch on all sides.

3. Glue Fiberglass Sheeting in Place:

Cut out a large triangle from scrap polymer cloth or fiberglass matting larger than the section cut from fiberglass sheeting. Glue it to the back face of the fiberglass sheeting using west system 105 resin and 205 Hardener. Allow the adhesive to cure before applying epoxy fillet around all sides of the hole.

4. Apply a Fiberglass Patch:

Cut a small patch from fiberglass cloth that fits over the rot. Coat one side of the fiberglass cloth with epoxy, then center and press it over it. Next, apply a layer of peel-ply to protect the cloth from being marred as you squeegee out excess resin. Allow time for the epoxy fillet to cure completely before using your boat again.

Apply a Layer of Peel-ply

5. Coat Hole with Epoxy:

Use epoxy to coat any exposed areas of rotted wood. Allow the epoxy to tack up before proceeding. Next, coat the exposed areas of rotted wood with west system colloidal silica thickener. Use a putty knife to mix it into the epoxy. Allow the thickened epoxy to become stiff enough to stand on its own, or use weights to hold it in place until cured.

6. Insert Wood Dowel:

Apply epoxy to the edges of the rot, then insert a wood dowel (or similar object) into the center of the rotted area. This will allow any excess epoxy to be forced out as it begins to harden. You can also tap lightly with a hammer or rubber mallet if necessary. Allow the epoxy to cure overnight.

7. Fill Rot with Marine-Tex:

To fix a hole in a boat, first insert a putty knife into the rotted area. Then, pack Marine-Tex expanding polyurethane foam insulation into the hole and force it up against the undamaged fiberglass above, using a chisel or screwdriver. Allow time for the foam to cure completely before using your boat again.

8. Cut Out and Replace Damaged Area:

First, you need to cut out the rotted area with a rotary saw fitted with a carbide blade. Make sure to vacuum away the dust created by cutting every few inches. Then, sand all sides of the replacement piece of wood smooth with 80-grit sandpaper. Next, apply epoxy to the edges of the rot, and fit the replacement wood into place. You may need to use screws. Allow time for the epoxy fillet to cure completely before using your boat again.

9. Fill All Holes With Epoxy Filler:

Use a caulk gun to apply epoxy into all holes. Use the putty knife to pack filler and then smooth out the surface with sandpaper. Allow time for the epoxy fillet to cure completely before using your boat again.

Use a Caulk Gun

10. Plug Damaged Wood With Epoxy:

If there is damage to your boat, you can cut plugs from scrap wood to fix it. First, make the plugs a little bigger than the damage. Then, coat the plugs with epoxy and fit them into the damage. If necessary, use a rubber mallet or hammer. Finally, allow time for the epoxy to cure completely before using your boat again.

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Some Helpful Tips and Suggestions

Here we have given some tips on how to repair rotted wood in a fiberglass boat.

1. Remove the rusted screws.

2. Make sure you cut out all of the rot around the screw holes, if it does not look like it will hold up after installation, then I suggest you remove more than just the rot that is visible to you.

3. After removing the rot, sand the area next to the hole with a power sander or hand-held sandpaper around 400 grit. This will remove loose fibers from the surrounding material and allow a proper bond between the patch and the surrounding surface.

4. Mix up your epoxy resin according to package instructions (mixing instructions are usually on the side of the epoxy resin can).

5. Mix your fiberglass cloth with resin, this will have to be done in a well-ventilated area, or I suggest using a respirator mask if you don’t have an open window or garage door nearby. If you’re mixing by hand, take turns stirring the mixture, wear rubber gloves, and get very little on your skin. If you’re using a mixer attachment on an electric drill, make sure the mixture is thin enough to drip off the end of the stirring stick easily.

Mix Your Fiberglass Cloth With Resin

6. Once the mixture is ready, apply it to the repaired surface. Make sure you cover up any surrounding areas that are not being repaired just in case the fiberglass resin leaks through, or some of it gets on an area that isn’t expected to be repaired.

7. When you have finished applying the patch, let it cure for 24 hours before using it in a boat.

Common Mistakes to Avoid When Repairing Rotted Wood in a Fiberglass Boat

You are using inorganic materials to replace rotting wood. There are many wood replacement products available on the market today, but they are not suitable for use when repairing fiberglass. The resins used in fiberglass boats are nearly identical to the resin in your skin. So when you cover up rotting wood with a hard and impenetrable substance like plastic or epoxy, you are sealing in the water that was previously draining out of the wood.

You are using the wrong type of epoxy. Regular epoxies will shrink and crack over time, leaving your boat with unsightly cracks. It would help if you used flexible epoxy or polyurethane when repairing fiberglass boats to ensure your finished product will last a long time.

Using a combination of inorganic materials and wood. Inorganic materials should be used to replace the rotted areas of your boat while using wood for other structural parts will ensure you have a solid and versatile product.

How to Fix a Rotten Mirror on a Fiberglass Boat

Fiberglass is a unique material. Unlike many other materials, it can bond to wood almost as if the two were made for each other. This makes fiberglass boats much more durable than those made from traditional wooden hulls. There are situations where repairs can be done to fiberglass without separating it from the wood.

Fiberglass Is a Unique Material

Yes, there are some limitations to this technique. The repair cannot be made by surrounding the wood with fiberglass resin and cloth, as that would cause a new layer of fiberglass to form on top of the old. This is especially useful for creating a structurally sound hull out of a damaged one without complete replacement.

It will also work if a hull piece is damaged and needs replacement. It will simply leave a seam, but it can be done nearly invisibly with fiberglass resin and cloth.

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Why Should You Repair Rotted Wood in a Fiberglass Boat

Many fiberglass boat owners only think of repairing rotted wood when there’s a problem. It’s important to look at the rot regularly and do maintenance to prevent problems in the future. There are several reasons why you should repair rotted wood before it turns into a big problem, including safety issues.

With fuel tanks, electrical components, wiring, and other systems located under the floors of many boats, there are a lot of hazards involved with having damaged wood. If you’re not able to see the extent of the damage by looking at it from outside the boat, you can’t be sure what damage is done underneath.

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Frequently Asked Questions

Can You Fill Rotted Wood with Wood Filler?

While it is possible to fill rotted wood with wood filler, the result is usually not desirable. This type of repair typically fails due to moisture and water infiltration that causes a deterioration in the structural integrity of the timber.

Additionally, using filler often leads to a more uneven surface that may not look appealing or functional. If you need to restore or replace any rotten boards on your property, it’s always best to call an expert for help who can recommend a suitable restoration procedure.

Will Epoxy Stop Dry Rot?

The epoxy may be a good solution for stopping dry rot, but it is important to note that this is not an easy or fast process. Epoxy is a type of resin that seals cracks and surfaces so moisture cannot enter and cause decay. It can take up to several months for the epoxy to fully cure, which means that the surface must remain relatively dry throughout this time period.

In areas where there has been significant water damage, epoxying might not be the best option because it will only cover up the problem instead of fixing it. Additionally, if you live in an area with high humidity levels, your epoxy sealant may slowly fail due to corrosion caused by mold and fungus growth.

If you are considering using epoxy as a treatment for your dried-out wood floors or furniture, please consult with a professional before proceeding.

Can You Epoxy Rotted Wood?

it will depend on the severity of the rot and the type of epoxy being used. However, some general guidelines that may help include soaking the wood in a mild solution of bleach and water before applying the epoxy, and leaving the treated area dry for at least two days before using any furniture or other objects on it.

where Should You Not Use Expanding Foam?

While expanding foam can be extremely useful in certain situations, it is important to use it cautiously. Some of the most common places where you should not use expanding foam include the following:

  • At home – Because expanding foam causes so much damage, using this product at home could trigger a lot of unforeseen damage. Expanding foam is best used in professional settings where there are adequate safety measures in place.
  • On windows – Expanding Foam can cause extensive window damage when sprayed on glass surfaces. Instead, use water or another non-damaging method to clean your windows.


The following is a guide on how to repair rotted wood in a fiberglass boat. Although this blog post will specifically deal with repairing rot in a fiberglass boat, the same principles can be applied when repairing rot in other wooden structures. Before beginning any repairs, it is important to assess the extent of the damage and identify all of the rotted areas. 

Once you have identified the damaged areas, you can begin removing the rotten wood and replacing it with new wood. To finish the repair job, you will need to seal and protect the newly replaced wood from moisture and future decay. We hope that this blog post provides helpful guidance for anyone who needs to repair rotted wood in their fiberglass boat. If you have any questions or concerns, feel free to comment below!

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