How To Remove Silicone From A Fiberglass Boat (3 Effective Steps)

Removing silicone from a fiberglass boat can be a challenging task especially when you don’t want to damage the base gel coat. It is quite hard to get rid of the stubborn silicone without affecting the gel coat.

This is indeed a difficult substance to get off any surface. Let’s find out how to remove silicone from a fiberglass boat.

People often claim silicone to be the best marine sealant for all types of leaks that may emerge on hulls or decks but unfortunately, it is not advisable to use silicone for fiberglass boats.

The substance doesn’t come off easily and could prove to be troublesome in the future if you ever think of repainting the vessel.

How To Remove Silicone From A Fiberglass Boat

Last year one of my neighbors bought a fiberglass boat. He wanted to repaint it. While preparing the surface he found out that the gel coat is contaminated with silicone. The previous owner had used the adhesive very generously on the hull.

He tried literally every method to remove it but in vain. The paint could not stick to it, no solvent could be dissolved in it so he just had to remove it manually.

The products that are commercially available for softening the sealant would harm the gel coat. They are intended to use on metal and other hard surfaces and are not safe for fiberglass.

You can not de-bond silicone easily, nothing can effectively remove the adhesive from fiberglass. He also tried some household solvents to loosen up the silicone, regrettably, all his efforts proved to be futile.

Finally, he bought a silicone caulking tools kit and a 3 M adhesive remover, then cleared off the surface physically with their help. The task was quite laborious but in the end, he succeeded in getting a silicone-free surface without damaging the gel coat.

Elbow Grease Method

Most people will suggest the elbow grease method. This method requires physical labor as the name suggests. The person is asked to use some scraping tools to take off the silicone.

The procedure is not only hard but also can cause damage to the fiberglass. It is also said to cut off the sealant bond with a sharp knife and then peel it off.

If you use steel knives, blades, or any other sharp tool to scrape off the silicone, you most probably will injure yourself, not to mention the gel coat finish.

This method does not work well. It can prove to be a disaster for your gel coat and fiberglass. In addition to this, a lot of patience and extra time is also required for the elbow grease method.

If you have spare time and are ready to do such a strenuous job then go for it. But all your efforts could be futile if the job is not done successfully.

Here in this article, we will discuss some steps by following them you will find your work easy and quick.

Soften the Silicone

Use of Products

Use of Tools

How To Soften It

The first and foremost step should be to soften the sealant. Silicon does not dissolve with any substance so it is very difficult to soften it.

However, there are certain solvents available in the market that can soften it and after that, you can easily remove it.

Some industrial silicone remover products are also available in the market but they should be used strictly under some professional supervision or by professionals only as they can be harmful to you.

Search for a solvent especially made to work on these bedding compounds, without harming the fiberglass.

Apply the chemical on the surface and leave it there for some time, at least 15-20 minutes. It will weaken the bond thus making it easier to scrape it off.

Before using any chemical on your fiberglass, it is of paramount importance to test it on a small hidden part of your boat to check whether the chemical is safe for your fiberglass or not.

It may dissolve the silicone sealant but can destroy the gel coat underneath it. Always read the instructions and warnings mentioned on the product and try to follow them.

Taking it off from a hard surface is a much easier job as compared to a fiberglass surface. Mineral spirits could be a nice choice for such a surface. Apply it on the hardware to soften it, and afterward, peel it off.

Another chemical that is quite effective in this situation is acetone. You can use this solvent to dissolve the silicone which will make your task a bit easier.

However, it is not suitable for all types of surfaces. Try using some household solvents to soften the sealant as they will be safer to use on fiberglass.

Isopropyl alcohol can do the job safely without harming the underlying surface but don’t try to rub the regular alcohol in your home on silicone, it would not affect you.

Denatured alcohol is also not suitable for fiberglass boats. You can use it on tough surfaces like tiles etc. but not on fiberglass boats. It can affect the base gel coat.

Another solvent from our kitchen is vinegar, which is also said to have the quality of de-bonding stubborn silicone. Apply a generous amount of the silicone, and leave it on for some time.

The sealant would not be dissolved, however, it would swell if you’re lucky enough and you can take it off by using a flexible knife.

This procedure does not work always. Silicone is a tough substance and removing it effectively from any surface is a big deal.

It is also recommended to heat the cured silicone sealant using a heat gun or a hairdryer. The silicone rubber compound can resist high heat, so no point in using it. It can damage the gel coat before it softens the silicone.

Products to Remove Silicone From A Fiberglass Boat

Taking off silicone from fiberglass is quite difficult but it is possible if you use proper tools and products specifically designed to remove sealants.

There are several debonding products available in the market. Try buying a product that is gentle on your fiberglass and does not penetrate the gel coat.

DeBond Mf 12 Marrine Formula is one of the products that work well on silicone and makes it relatively easier to get rid of it. Always test on a patch before applying it to the whole surface.

DSR-5 adhesive remover that can be used on fiberglass boats without getting worried about the gel coat. It is effective and safe to use on metals, wood, plastics, fiberglass, and gel coat.

Goo Gone Adhesive Remover Spray Gel is also said to be safe on fiberglass and helpful in softening silicone sealant.

3M General Purpose Adhesive Remover also does not cause any damage to the gel coat.

Spray on the affected area with the remover, and leave it there for a few minutes. The sealant would loosen up, now you can pull it apart.

Repeat the process if needed. Hopefully, the cured silicone would be gone within minutes.

Tools to Remove Silicone From A Fiberglass Boat

After the sealant has softened a bit, break the bond with a plastic scraper and try to cut it off as close to the surface as possible. For this slicing technique, you will need a purpose-built tool kit.

Cut off the bulk away. Pull apart as much silicone as possible and scrape off the remaining that is still present on the surface with the help of a plastic scraper.

Although a tedious job but can be trouble-free if the right type of equipment is used.
An adhesive remover along with a putty knife or a scraper made out of plastic would do the chore perfectly.

A fillet knife can also do the task to perfection as it is flexible and we can use it on curved surfaces. So to remove the bulk of sealant, use a scraper but in small, curved spaces make use of a flexible knife.

Several tool kits in the market will serve the purpose. You need to buy the one which meets your requirement.

To name a few:

1. 3-in-1 silicone caulking tools

2. EHDIS 1.5 plastic razor

3. Double-edged plastic razor blade scraper knife

4. Dynatron 3-pack spreaders

5. Premium boat scuff erasers

How to Remove the Residue

Even after taking off most of the silicone, a thin layer would still be present there. To get rid of it, apply another layer of remover.

Soak a piece of cloth or rag with the sealant remover and rub it on the silicone layer. Keep it there for about 15 to 20 minutes and when it gets softened, remove the silicone layer with a plastic scraper which will not cause any damage to the fiberglass.

Sharp, metallic tools can harm the gel coat so try to avoid them and stick to the plastic ones.

Next, it’s time to smooth away the place and remove the tiny bits of silicone if any. Scrub the surface with sandpaper or an abrasive hand pad to clear it off from any remnants of silicone left behind.

Finally, spray a little acetone or denatured alcohol and wipe off the surface. Your fiberglass boat is ready to be re-painted or re-bedded.

Always test the chemicals on a hidden patch of your fiberglass boat, if the solvent is not damaging or staining it then go for it otherwise replace it with a milder option i.e. isopropyl alcohol.


Silicone sealant is a stubborn substance that can not be removed easily, however, if you use the right technique and appropriate tools, you’ll be able to clear off your fiberglass boat from this adhesive.

Now you know how to remove silicone from a fiberglass boat.
So, what are you waiting for?
Go and get down to work!

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