How to Clean a Fiberglass Boat + What You’ll Need

how to clean a fiberglass boat

You may have just purchased that fiberglass boat you've always wanted, and you've gone on a few trips with it. Or you haven't used it in a while and now you'd like to take it out on the water again. Then you notice how much dirt has gotten on your boat, not to mention some discoloration, and now you'd like to learn how to clean a fiberglass boat.

This guide was made with fiberglass boats in mind for boat owners that want a cleaner boat, and for that our first step would be understanding a few things about fiberglass.

Understanding Fiberglass

Fiberglass is an amazing structural material, being light yet sturdy hence it's a perfect material for building boats, but it gets most of its strength from the resin mixed in with it.

A special outer layer of resin called a gel coat is what keeps the boat hull watertight, shiny, and well protected.

This gelcoat is waterproof obviously, but it can be dissolved or weakened by the occasionally harsh boat cleaner, so to make sure you end up with a stain-free yet absolutely pristine fiberglass boat, here are a few things to keep in mind.

What Will You Need to Clean a Fiberglass Boat?

To save you the hassle of searching for the right tools, we've compiled a list of the bare necessities and some tips to properly clean a boat.

1. Boat Juice Cleaner Kit

boat juice cleaner kit

This fiberglass boat cleaning kit comes specially formulated with two different types of boat cleaners, an exterior version for the boat hull, and an interior version for the deck.

2. Star Brite Boater's Combo Set

star brite boaters combo set

This reliable combo set from Star Brite includes a brush, sponge, and scuff remover and is ideal for scrubbing out the toughest of stains on your deck.

3. Boat Cleaner Microfiber Set

boat cleaner microfiber sponge bucket and microfiber wash cloths

You're also going to need a soft microfiber cloth and a microfiber sponge set which is an absolute necessity for all your cleaning needs and is perfect for fiberglass boat cleaning.

4. Star Brite Non-Skid Deck Cleaner & Protectant

star brite non-skid deck cleaner and protectant

A stain remover from Star Brite will do amazing work for cleaning fiberglass and other painted surfaces. It specifically states that it's safe to use for fiberglass and will make sure you don't damage the gelcoat no matter what.

5. Sun Joe Pressure Washer

electric high pressure washer

An easy to use, and reliable pressure washer like this one, is key to your fiberglass boat cleaning needs.

6. Meguiar's Marine Wax

meguiars marine wax

To protect a boat's gelcoat after cleaning you can use Meguiar's waxing solution to help protect that surface from harmful UV rays and water-line stains.

7. Marine Polish by Star Brite

star brite premium marine polish

If you want to give your boat a little bit of shine or just want to get rid of some buildup after several cycles of waxing, give this premium marine polish from Star Brite a try.

8. Portable Buffer by Popoman

buffer polisher

This Brushless Cordless Polisher Set works well as both a polisher and buffer and would make your fiberglass boat that much cleaner.

Fiberglass Boat Cleaning Tutorial

Now we can move on to the actual process and here are a few tips.

Get the Stuff

We've compiled a list above for all your fiberglass boat cleaning needs, from tools such as microfiber soft cloth and brush set, cleaning products, including commercial boat soap and boat cleaner, down to baking soda and vinegar to make your boat's surfaces spotless.

It goes without saying that you're also going to need a source of clean water, especially when you're washing huge areas like the exterior of the fiberglass boat and the deck.

Wash the Boat

The first step and primary way to clean a fiberglass boat is washing it. Spray the deck and sides down with water from a pressure washer to remove dirt and grime, and wet the remaining filth for the next step.

You can use just about any boat cleaner that says it's fiberglass boat safe. This is important because we don't want to damage the gelcoat.

For boat canvas, mild soap mixed with water makes a good cleaner for this material. Along with some brushes and scrubs make sure that every nook and cranny on the deck is clean, and spray it down one more time to reveal the tougher stains.

Remove Stains

Washing the boat along with some soap and water may have made the boat cleaner but stains still remain, so to remove them whether it be on your hull or on your deck, while making sure we don't harm the gelcoat, here is another set of tips.

Stains vary depending on their source, from rust and mildew common to the deck, down to water spots and slime on the exterior of your fiberglass boat. Thus it is difficult to find a boat cleaner that can clean all of these at once.

You can look for stain removers for specific stains, or use homemade cleaning solutions such as baking soda and vinegar, then put them in spray bottles and label them with the appropriate stain.

The next step is to spray a soft cloth with your boat cleaner, then wipe away the stain. Should that be insufficient you can use a brush and scrub, but make sure to use the ones listed above to avoid gelcoat damage.


Rinse the deck and the hull, that you've cleaned previously with some clean water. Make sure you give the fiberglass boat a thorough washing so that the boat cleaner you've used gets washed off.

Wipe the entire cleaned surface with a soft cloth and let it dry, ensuring that no area stays wet for the next process.

Waxing and Polishing

Use some rubbing compound or polish to prepare the surfaces for the final step a.k.a the waxing job.

Try not to go overboard on using rubbing compounds as they are abrasive and actually remove a thin layer of fiberglass to prepare the surface for waxing. It also helps to use products designed for fiberglass use only.

Once polished you need to buffer it up a bit, just to remove the excess, then finally do some waxing and more buffering on your fiberglass boat.

Waxing Buildup Removal

This step is unnecessary if you don't have any discoloration or wax build-up but for those of you who do, you're going to need to restore the boat's surface.

The important part here is the cleaner you're going to use. Some scrubbing solutions are harsh chemicals that might not be entirely safe to use, while others like boat polish tend to be very abrasive and will remove the wax quickly, and scratch the gel coat when you're not careful. Other cleaning products may be okay for fiberglass but may ruin other surfaces such as vinyl, so do keep that in mind.

To remove it in a safe surefire way, then I would suggest that you use vinegar instead. Not only is it non-abrasive and absolutely safe for your fiberglass boat, but it's also environmentally friendly, and the vinegar removes it without hurting the fiberglass underneath.

Is Using Bleach a Good Idea?

cleaning a fiberglass boat

Long story short, it's a hit or miss.

Some dilute bleach with water to make it less damaging on the boat, and although it does work to some extent, this method varies from one boat to another. This is because different boats have different gelcoats which may react badly with the bleach.

Bleach is not environmentally friendly and is detrimental to the marine environment, thus you better be careful as a splash of bleach on materials such as vinyl can ruin it, not to mention the long-term effects it has on the gelcoat of the fiberglass itself.

It can also irritate the skin and lungs when not properly protected, and melts through any waxing job down to the gelcoat of the fiberglass.

Safety Tips

Whenever you start your boat cleaning session, always make sure to wear proper protective equipment.

Rubber gloves and eye protection are a bare minimum. It also helps to wear splash-proof outer clothing to prevent chemicals from irritating your skin, and a proper face/gas mask to prevent inhalation of debris and toxic gasses.

A well-lit and ventilated environment and some kneepads wouldn't hurt either.

Frequently Asked Questions

What is the best thing to clean a fiberglass boat with?

In a nutshell, water mixed with some fiberglass boat soap or your favorite cleaning solution works well enough for most filth without ruining the fiberglass surface. We've written a few tips about cleaning fiberglass boats above, so be sure to check that out.

How do you remove stains from a fiberglass boat?

Say you've already washed your boat with water and soap, yet you haven't removed the stubborn stains made of rust, mildew, or layers of oxidation, feel free to use a dedicated stain remover made for fiberglass boat cleaning to wash off those tough buggers.

How do I make my fiberglass boat shine again?

When you've already done cleaning the dirt and stains and it's just not shiny enough for you, then it may be necessary to restore the boat by using some commercial fiberglass powder cleaner, or rubbing compound and some waxing, together with a good buff, and voila, shiny boat.

How do you remove wax from a fiberglass boat?

Get some wax remover or polish, and use it to remove all the build-up from previous applications. For more details we've written a guide above, so check it out!

How often should you clean the fiberglass deck?

After every use. You don't have to do a thorough cleaning but you should at least spray it down with a pressure washer just to get rid of the surface grime. Also, assuming your boat stays in the water 24/7, then you should do some thorough boat cleaning, at least once a week.


To the proud boat owners out there reading this, we hope this guide has given you some tips on how to prolong the life or enhance your boat's aesthetic. For other things you can do you may want to check out our guide on painting a fiberglass boat.

As a boat owner or boat cleaner, the next time that sparkling clean boat goes on a marine adventure, you should fear neither stain nor water line, because you now have the confidence in knowing how to clean a fiberglass boat.

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