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How can I Repair a Fiberglass Boat?

Diana Bocco
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Updated: May 23, 2024
Views: 115,714
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One of the best qualities of a fiberglass boat is how easy it is to repair. While a damaged wood boat requires expensive and intricate work, a fiberglass one can usually be repaired with just a few materials, even by people with only basic knowledge and skills. Another great quality of a fiberglass boat is that, once repaired, it looks as good as new. After the new layer of fiberglass dries, it becomes part of the boat, rather than a superficial patch.

To repair a fiberglass boat, start by cutting away the damaged area. To make sure you're stripping away all the damage, always remove an area at least half an inch (1.27 cm) larger than the damage you see at first view. This type of boat is always waxed, so before you attempt to repair the hole, wash the area with a solvent. Getting rid of the wax will not only make the process easier, but it will also prevent the inner surface of the boat from cracking and weakening. Next, using a disk sander, grind the area surrounding the hole until you get a distinct, uniformly dull look on the surface, and then apply a heavy coat of paste wax.

There are several materials you can use to repair a fiberglass boat, but for the inexperienced boat owner, it is best to buy a repair kit. Start by taping a piece of Formica or Plexiglas to the inner surface of the boat, making sure to cover the hole thoroughly. This will serve as backing. Next, mix all the materials that come in the kit – usually some type of resin and a hardening agent. Fill in the damaged spot until it's level with the hull of the boat, and then smooth the area with release paper or cellophane for a high-gloss finish.

If your fiberglass boat only has superficial damage, such as scratches and cracks, sand the area and remove the wax with a solvent before applying a store-bought plastic filler such as Gelcote. Wait for the plastic filler to cure before applying another coat. Two coats are usually enough to repair standard damage in the typical fiberglass boat. Finish by sanding the filler to a smooth level and follow with a coat of primer.

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Diana Bocco
By Diana Bocco
Diana Bocco, a versatile writer with a distinct voice, creates compelling long-form and short-form content for various businesses. With a data-focused approach and a talent for sharing engaging stories, Diana’s written work gets noticed and drives results.
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Discussion Comments
By anon925114 — On Jan 09, 2014

How do I build up a low spot on a fiberglass keel when repairing it?

By anon281237 — On Jul 22, 2012

I have a old fiberglass join boat that I am restoring and I need to know what type of paint and primer I need to use on the outside and bottom of the boat.

By anon193008 — On Jul 03, 2011

my boat has rot on the inside of the back where the outboard bolts to. how can i fix that?

By Buck — On Apr 27, 2011

I inherited a 1972 Starcraft 14' fishing boat. the deck was rotted bad. While cutting out the rotted sections I got to close to the hull, yep I cut a 8" long slit in it. What do I need, how do I fix it? Help, please.

By anon138618 — On Jan 01, 2011

I have a 27' Bayliner Sailboat that has a cabin. I want to redo the ceiling in smooth fiberglass as there was vinyl on the ceiling that was coming down. I have researched trying to find materials to use to do the smooth fiberglass ceiling and walls half way down the boat, but have had no luck. Do you have any ideas? Erin

By anon106713 — On Aug 26, 2010

what kind of backer can I use to form the corner,

because everything I try to use cracks on the bend

that was damaged about 4' long on the port side? and also west system or resin 6631 iso with a slow hardener for working time.

By anon101920 — On Aug 05, 2010

I'm new to this site, but I liked what I've seen/read; so I thank you for allowing me to post these questions.

I just purchased an 18' - 1987 Regal/Sebring,cuddy cabin fiberglass boat as a project/hobby boat. As far as the fiberglass goes, the bottom, stern, hull and the whole floor are solid. The cuddy cabin is firm as well.

The problem is the boat sat out for a few years with no cover. The side panels were shot, and were removed. I want to make my own.

I've read that starting off with plexiglass as a backing could suffice. I have a few questions if anyone can help me out. How thick of fiberglass would be good for this. What is the best way to make it stick to the inside part of the fiberglass, (super glue?) Before I tackle it from outside, how safe is it to fiberglass a wood support on the inside of it (to hang wires and whatever)?

Thank you all for reading and for any response you might have. Sorry for the book.

By anon94543 — On Jul 09, 2010

I got a 2000 glastron that has a hole in the hull towards the back right in the center. When looking at this it looks like little blocks of wood glued together on one side and a fiberglass mold on the other side. Its split down the middle. The fiberglass that broke is only about 3/8" thick. Can I just fiberglass over it and be done with it? Because the fiberglass isn't actually a support of the boat right? it's just a skin. Any help would be greatly appreciated. Thanks.

P.S. It's a fiberglass I/O if that helps any at all.

By anon94219 — On Jul 07, 2010

I have a small fiberglass rowing boat that was used for fishing but where you put the oars on the one side. the fiberglass has broken, leaving a small hole in the lip of the boat.

How can I repair this so I can use it again? I don't want it to cost the earth to repair. Hope you can help.

A. Dallas

By anon91867 — On Jun 24, 2010

Me and my cousin found a really old boat in the river, and took it up to the house, and the entire bottom is rotted wood because it's been underwater so long. How would we go about repairing it? We both have almost no knowledge about boats.

By anon91299 — On Jun 21, 2010

I've got damage all the way down the corner on the bottom of the hull. Only one spot has a small hole in it. How do I fix this? There is no way to get to it from the inside unless i tear the whole boat apart. it is an 80's model.

By anon90791 — On Jun 18, 2010

Q: my problem that I run into is that it will take about a week for my resin to dry. I think I need to add more hardener in with my resin. And what should I use as a backer for my corner repair. Please help!

A: Yes, you need to use more catalyst. This can be done by weight or a percentage, depending on the type you are using.

Backer? you could apply some styrene foam and build over that.

Q: How do i get the textured look instead of the smooth look?

A: Use a textured roller, available at fiberglass shops.

Q: Could anyone tell me can i paint my fiberglass boat with gloss, or will that harm the fiberglass?

A: No, it won't harm it; paint away!

Q: What type of saw do I need to use to cut through the clear coat and gelcoat without a lot of spider cracks?

A: Any saw, as long as it's got fine teeth - the finer the better.

Q: I have a fabric kayak that needs to be repaired. is there such a thing as fiberglass fabric?

A: Yes, it's also called 'glass mat' or 'glass cloth.' You wet the surface with resin, place your mat, then roll the air out, and apply lightly, a coat of resin over the top so that it penetrates.

Q: I've got a boat that is five years old. it has got small cracks, like the bench is detached from the floor, like a line crack. the angle is 90 degrees. how is this repaired and what do you put in it? can i do it myself?

A: Yes, use a good quality matting - and use it like a plaster. Go down over the bench and also don't forget to do under the seat also.

Q: What if I'm trying to patch a hole in the bottom of the boat, working upside down? Will all the patching materials fall out before they set enough to stay in place?

A: No, just wet the surface with resin that is thickened with TALC or Q-CEL. This will make the resin thicker, and enable you to work upside down.

Once you've wet the surface with the resin, apply the glass matting - then work resin into it and use quick release cloth or cellophane to make it smooth and tidy.

Hope these answers help you all. - Chris

By anon86121 — On May 23, 2010

I have a 12ft jon boat and I need to repair a corner pc and I need some instruction on how to do this. I have made repairs on this boat before. my problem that I run into is that it will take about a week for my resin to dry. I think I need to add more hardener in with my resin. And what should I use as a backer for my corner repair. Please help!

By anon85163 — On May 19, 2010

how do i get the textured look instead of the smooth look?

By Jillu2 — On Apr 09, 2010

Will marine tar seal a fiberglass curragh ?

By anon74031 — On Mar 30, 2010

Could anyone tell me can i paint my fiberglass boat with gloss, or will that harm the fiberglass?

By trela — On Feb 22, 2010

What type of saw do I need to use to cut through the clearcoat and gelcoat without a lot of spider cracks?

By anon47534 — On Oct 05, 2009

I have a fabric kayak that needs to be repaired. is there such a thing as fiberglass fabric?

By anon44571 — On Sep 09, 2009

hi my problem is i've got a boat that is five years old. it has got small cracks, like the bench is detached from the floor, like a line crack. the angle is 90 degrees. how is this repaired and what do you put in it? can i do it myself?

By anon44542 — On Sep 08, 2009

I need help fiberglassing 370 carver aft cabin

that was hit hard in the starboard corner. I can't seem to find any material that will bend around the corner to make a mold of the damaged glass. --Dave

By anon44331 — On Sep 07, 2009

What if I'm trying to patch a hole in the bottom of the boat, working upside down? Will all the patching materials fall out before they set enough to stay in place?

By anon42962 — On Aug 24, 2009

Hi I have a 1950's fiberglass fishing boat. It was my boyfriend's grandfather's boat. My question to you is:

The floor is just fiberglass and it's just a bit thin now. I would like make this small lake boat useable again in honer of Puz {Grandfather] and just enjoy it for what it is. A fishing boat. I'm not going to sink a lot of money into it but I am willing to work hard to make this boat last another 60 years. What would you do? Lynn

By anon41593 — On Aug 16, 2009

Yes you can fix all of these problems. Enough time, and preparation, and lots of patience and your boats will look brand new. I'm repairing the runners below my floor right now. It involves a lot off cutting out old wood and glass, fitting new wood and re-fiberglassing the works. Its a lot of work but when done it will be worth it.

I found the problems because the gelcoat had started to crack. Once I fix the structural parts of the boat I'll attempt the gelcoat repair. Any advice on gelcoating?

By anon40717 — On Aug 10, 2009

Hi. I hope someone out there can help/advise. Is it possible to repair fire-damaged fiberglass boats and if so, is it the same process as previously discussed eg: remove damaged areas etc and rebuild? Many thanks --MJ

By anon30561 — On Apr 21, 2009

I wonder if someone can help me? I have a fiberglass cabin boat(it's a microplus 501). A few years ago it ended up flipped over on its cabin and crushed in. The cabin is still mostly attached but has come apart at a couple of points.

Is it possible to repair the cabin myself and have the boat back in its normal strength? Also how would I go about doing it?

Alan

By enschwing — On Aug 13, 2008

How do you fix a hole in the hull of a fiberglass boat?

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Diana Bocco
Diana Bocco
Diana Bocco, a versatile writer with a distinct voice, creates compelling long-form and short-form content for various...
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