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How to Clean Fiberglass Boat Deck?

Written by J. Harvey / Fact checked by S. Numbers

how to clean fiberglass boat deck

It is no joke to own a boat. The insurance, docking fees, and registration are quite expensive, too. Not to mention, it needs regular maintenance to keep it looking new and in good condition.

It would help if you were minding not only some fees but also the upkeep of its fiberglass deck (and hull). Maintaining it can reduce maintenance and repair costs, so learning how to clean fiberglass boat deck is advantageous.

Today, I’m going to show you how to do it properly (and quickly). But then, I want to show you another way without using any bleach to clean it. While most boat owners will tell you that using bleach is the best way to clean the deck, you can take this alternate route.

In my experience, I find it easier and faster to deal with the stains with a non-stick and gentle deck cleaner before finally applying some finishing scrubbing to polish the surface. Come aboard, and let’s get started!

Things you will need

  • Deck cleaner fluid
  • Pressure washer
  • Long deck brush
  • Clean rug or cloth
  • Bucket of water

Steps On How To Clean A Fiberglass Boat Deck


This method applies to both beginners and advanced boating enthusiasts because it doesn’t require any complicated steps and long process. It will help to clean not just the deck but also the sides of the boat. Following all these steps closely, you’ll restore the lovely and stain-free appearance of your deck and hull.

Step 1: Get your things ready!

Before starting this task, I recommend you go ahead and shop for the items mentioned above, including a good deck cleaner you will find on Amazon. And don’t forget, you also need your pressure washer, hose, some old cloth/rugs, and a pair of gloves. For buffing the surface later, get your buffer ready.

Step 2: Start pressure washing the sides and decks.

You need not use your cleaners just yet. At this stage, prepare the surface for cleaning. Brush down once, then pressure wash it, and remove the debris, mold, mildew, or whatever substances have formed in the deck. Doing this, you can speed up the process of cleaning the deck.

If you don’t have a pressure washer yet, you might want to invest in one that you find on Amazon or any other online marketplaces for that matter.

Step 3: Wet the surface of the fiberglass.

During the pressure washing, you might have left some gaps dry. It will help if you wet the surface again to ensure that all of it is. That will leave a film of water all over, and that would help in the next steps. Alternatively, you can use a hose to wet the fiberglass if you’re near a water supply or clean down with a bucket of water.

Step 4: Spray deck cleaner on the deck and hull.

Spray, or put some deck cleaner onto the wet fiberglass deck. Move it around to ensure equal distribution across the surface. Recheck it, see if you’ve sprayed the entire fiberglass deck and if you left some spots without the cleaner.

Step 5: Take a little break, and let the deck cleaner sit for three minutes (or longer if possible).


Let the cleaner settle for a few minutes or longer for better results so that the cleaning agents can work effectively in lifting and breaking up the mildew, mold, dirt, and other stains. Ten minutes can also work. It will let the deck cleaner cut into the unwanted dirt and stains.

Step 6: Start brushing the deck.

Get your long brush, and then begin work. Scrub the dirt, stains, mold, and mildew. Using a deck cleaner, you don’t have to scrub hard to lift any dirt residues because it can lift them without any hassle. Notice that after cleaning, the deck will have this non-slip surface that shines.

The deck cleaner will also leave a layer of protection. It is safe for fiberglass boats, so you don’t have to worry about leaving any damage or degrading the boat’s surface. Some deck cleaners are also great for other boat surfaces – painted or metal.

Step 7: Spray or hose down the deck.

Use a hose to water down your deck once more to remove any remaining debris. If you have a pressure washer, you might want to use it but in a lower setting. Do not use a higher setting, or that will remove the protective layer.

You can use a water sprayer if you have it, or a hose if none. However, the latter can take a much longer time, although it works just fine.

Step 8: Check out the hard to reach areas and scrub them.

Using a clean cloth with some deck cleaner, you can scrub small corners, gaps, and other hard-to-reach areas to ensure everything will be cleaned.

Step 9: For a shiny surface, buff it.

This is an additional step if you don’t just want to clean but polish the surface to leave it shiny. You can use a buffer in this step. You can find some buffers and polishers and brushes in many boating shops and stores to make your job easier. Also, you can find a complete kit that includes a polisher and a buffer.

Pro Tips

  • Scrub the fiberglass surface before using a deck cleaner to remove long-standing dirt and residue. Doing so, you will not also need to use any bleach.
  • Clean the deck after every use by spraying it down if your boat stays in the water 24/7. But then, you do a thorough cleaning with a deck cleaner once a week.
  • Use the deck cleaner as directed on the label to work well and produce great results. Choose one that is tough to get rid of the stains but gentle enough not to damage the surface.


Your boat will look dirty and eventually lose its value if you don’t maintain it properly. It’s why you need to learn how to clean fiberglass boat deck, especially if you’re using your boat more often, or it stays 24/7 in the water. Cleaning it properly using the steps outlined earlier, you can maintain its top condition while also not using bleach or any nasty chemicals in the process.

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