What oxidation looks like on a fiberglass boat hull

If you have owned a fiberglass boat for a while, you know that over time the finish may become dull or faded.  This is especially likely if you have a dark colored hull.  That beautiful boat that once looked shiny and new is now looking rather old and boring due to something called oxidation.  The good news is that, in most cases, you should be able to treat your hull to get it much closer to that original showroom finish.

In this article, I briefly describe the process of restoring a fiberglass hull that has oxidized and identify the products you will need.  I’ve also included a link to a video where I show how I restored the finish on my personal boat that had a considerable amount of oxidation in one corner.

What is Oxidation

Oxidation is a chemical process in which the gelcoat breaks down due to exposure to UV rays and other environmental elements.  Microscopic cracks form in the gelcoat which produces that dull, chalky, appearance.

Key Things to Know About Gelcoat

Always use the least aggressive product that you can get away with

Gelcoat is a pigmented epoxy or resin applied to the outer surface of a fiberglass hull.  It provides that colorful, glassy, appearance and protects the hull from moisture and UV rays.  Overtime, the gelcoat can breakdown and oxidize due to extended exposure to sunlight or other environmental elements.  The best way to prevent this is to keep your boat properly waxed and covered when not in use.

The gelcoat layer is very thin – only about 1/32″ or less on most boats.  Therefore, when treating an oxidized hull, you need to be careful not to strip away more gelcoat than is necessary to avoid prematurely aging your hull.  Once the gelcoat has been completely stripped away, you will not be able to restore the finish without doing something major like painting your hull.  Therefore, when restoring your fiberglass boat finish, you should always use the least aggressive product that you can get away with.

The Process

Restoring the finish is not difficult or complicated but it may require a bit of “elbow grease”.  The process is as follows:

Step 1: Clean the Hull

Thoroughly clean the hull of your boat to remove any dirt and/or marine growth.   A power washer and some dawn dish soap is ideal for this.  Though Dawn will strip away any residual wax, that is fine because we will be applying a fresh coat of wax at the end of the process.

If your hull has a scum line that is difficult to remove, try something like this Starbright Instant Hull Cleaner to easily remove it.  For tougher stains or marine growth, you will need something more aggressive like this MaryKate On&Off Hull and Bottom cleaner.

Step 2: “Polish” the Hull with an Abrasive Material

The term “polishing” is often confused with “waxing” but are really different things.  Adding to the confusion are some products that are labeled as a “polish” but are essentially a synthetic wax.  However, “polishing” in this case really refers to products made with minor abrasive materials or grit to treat imperfections (stains, minor scratches) and gently strip away some of the gelcoat.  Think of it as exfoliating your skin.  The goal of polishing is to remove the dull, outer layer of gelcoat that has been oxidized to expose the healthier and more vibrant layer underneath.

There are a variety of products to choose from depending on the severity of the defects or oxidation of your hull.  And, some are “single purpose” products while others are multi-purpose and will “polish” and “wax” at the same time.

To find the right product for your situation, check out my product selector tool.  Choose “Restore finish” for the goal and then select either “Single Purpose” or “Multi Purpose” for the function to display the applicable products and prices.

As mentioned earlier, you should always use the least aggressive product you can get away with to avoid prematurely aging your hull.  This might require a bit of experimentation on a small portion of your hull to figure out which product is needed in your situation.  Below are the products that I tested on my boat.

Light to Moderate Oxidation

The Starbright “Cleaner Wax” is a multi-function product that is intended for minor oxidation issues.

Moderate to Heavy Oxidation

This Starbright “Restorer Wax” is a more aggressive product to treat more severe (moderate) levels of oxidation.  This too is a multi-function product (polishes and waxes).

Heavy Oxidation

For tough cases, you need something with considerably more grit such as this One Step Compound from Meguiar’s.   Unlike the products above, this is a single-function product and therefore does not contain any wax.  Therefore, if you go this route, you will need to also do step 3 (listed below) to apply a final protective layer.

Regardless of which product you go with, it will take a bit of “elbow grease” to work it in and remove the dull gelcoat layer.  If you have a large area to treat, then you might want to get yourself a random orbital or DA (dual action) polisher to make the job a bit easier.  Here is the one that I use. It is not “professional grade” but is fairly inexpensive, gets excellent reviews on Amazon, and is perfectly suitable for the one or two times a year that I use it.

Step 3: Add a Protective Wax Layer

If the product you chose for Step 2 was not a multi-function product containing wax, then the final step is to apply a coat of wax to protect the finish that you worked hard to achieve.   You will want a marine wax for this that is designed to adhere to a fiberglass surface.  There are two primary types to consider.  A natural wax, made of Carnauba, will give you the best possible shine.  However, a synthetic wax or polymer, bonds better and lasts considerably longer which is what I use.

Natural Wax

Many consider this to be the best Carnauba wax available for boats and it achieved superior ratings in a previous BoaterInput study.

Synthetic Wax (polymer)

This product from Starbright provides 2 to 3 times longer protection than a natural (Carnauba) wax.


In this video, I show how I restored the finish of my 11 year-old boat that had oxidized in one corner due to excessive exposure to sunlight.   You will see how I tested three different products in the beginning before deciding which one to use.

If your fiberglass boat has lost its once vibrant appearance, take heart in the fact that there is a good chance you will be able to fix it.  As you learned in this article, the process is not complicated or difficult and so most people should be able to do it themselves with the right products.  However, it does take a bit of time and effort.  But, in the end when you restore the look to its former self, it will all seem worth it.

Jerry Mona - BoaterInput

About the author

Jerry Mona is an avid boater and angler and long-time boating industry insider. With over three decades of experience, he is often considered to be the leading research expert with boaters and has helped numerous manufacturers and trade associations to understand the needs, wants, attitudes and behaviors of boaters. He now shares many of his insights about boats and boaters for free on his BoaterInput.com website.

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