We all know that the upkeep of a boat can be very laborious. There’s registration, docking fees, insurance and that doesn’t even cover the cost of any repairs done to the boat itself. Despite all of these fees, I wouldn’t have it any other way. The feeling of taking my boat out on the water is like nothing else. I named my boat, “Solitude” for a reason after all.

One way in which you can keep your boat in good shape, leading to reduced maintenance and repair costs, is to take clean the fiberglass, deck and hull regularly.

Handy Hint: If you don’t do proper maintenance, your fiberglass deck can become moldy, costing you anywhere from $500 to $3,000 dollars for a replacement.

But how exactly do you go about cleaning a fiberglass boat, deck, and hull? To set you up for success, I will go through each and every step that I have found to be useful when cleaning my own Catalina 22.

Cleaning your boat’s fiberglass deck or hull without bleach

The majority of boat owners will tell you that the only way to clean a fiberglass boat and deck is with constant scrubbing and bleach. I never use bleach.

I have found that it is far easier and safer to tackle stains with a non-stick deck cleaner followed by any touch-up scrubbing that your boat needs.

There are a number of tools that can help you with the cleaning process, many of which boat owners will swear by.

To make your life easier, I recommend that you invest in the following products:

What you will need

How to clean a fiberglass boat in 8 steps

The instructions below will work for any form of fiberglass boat cleaning include sides and deck. I get insanely good results using this method.

1. Buy the essentials products

The first step in cleaning your fiberglass boat, deck, is to get the right products (you can see my shopping list above which includes the Star Brite).

In addition, make sure that you also have a deck brush, hose or pressure washer, old rags, gloves and a buffer for polishing up afterwards.

2. Pressure wash the fiberglass deck and sides

Before I even get my cleaning products out, I will do a once over brush down then pressure wash. This will remove a lot of mildew and debris from the fiberglass deck.

If you don’t have a pressure washer, I recommend the Sun Joe (view Amazon prices) that you see in the image. It’s a great price and very powerful.

3. Wet the fiberglass and deck down

The pressure washer will leave some wet, but if you’ve left a gap between the pressure washing and this stage, you should wet the fiberglass deck down again, so it has a film of water across it.

You can either use a hose if you have a tap or water supply nearby, of simply throw a bucket of clean water down.

4. Spray Star Brite deck cleaner on and brush around

Put some of the Star Brite cleaner (see Amazon reviews) down onto the wet deck, and move it around using a deck brush. You want to make sure that it is evenly distributed across the fiberglass.

Leave it to settle for three minutes, as this allows the chelating agents to get to work. They actually start to life up dirt and mildew or mold stains, breaking them up.

Handy Hint: Star Brite say leave it for 3 minutes, but I recommend to let the product cut into any stains or unwanted dirt by letting it rest longer. For better results, I have found that 10 minutes does the job.

how to clean a fiberglass boat using star brite cleaner

Once you spray this cleaner down it will start to list dirt and mildew off the fibreglass deck.

5. Agitate with your deck brush

Once the 3 minutes are up, it’s time to get to work with your deck brush. You can scrub away the dirt and mildew really easily now, and you might not even have to scrub that hard.

Star Brite is really effective and will do a lot of the hard work for you.

It will even leave you with a non-slip surface, giving a layer of protection that is safe to use on fiberglass boats, plus any vinyl such as seating, metal or painted boat surfaces.

6. Hose or spray down the fiberglass deck

If you have a hose, use that to now water down the deck again to get rid of any debris that your brush hasn’t pushed away.

You can use your pressure washer instead but keep it on a lower setting as you don’t want to take up any of the protective non-slip layer the Star Brite has left.

Using a high-pressure water sprayer is preferred for most boat owners as it is quick and effective. If you only have a normal hose, that works just fine, though it may take you longer.

7. Touch up any hard to reach areas with a cloth

You might find that you still have some dirt in corners and gaps.

If there are areas that could use some scrubbing, use a clean cloth with some Star Brite, pushing your finger into the space.

8. Buff and polish up for a great shine

An optional step is to follow up any cleaning with a good buffer.

Boating shops sell polishers and buffers, including waxing brushes that will make your job easier.

I love the Marine 31 boat polish and wax, and they sell a kit that comes with a buffer and polisher too (see the Amazon reviews).

The results you will get from Star Brite

If you apply and use it as directed on the bottle, it will get to work really well, producing a great foam that will take up the most stubborn stains from the fiberglass. It cleans not just fiberglass elements, but also painted and moulded decks.

By scrubbing with a brush before you use it, you will make it even more effective. It requires a lot less effort than other fiberglass boat cleaning products I have used, including nasty, chemical-laden bleach products.

For a 28-foot boat deck, you will need most of the bottle that I recommend in this guide on how to clean a fiberglass boat and deck.

Watch this video to see an example:

How to clean a fiberglass boat (related questions)

Now that you know each and every step that goes into properly cleaning and maintaining your fiberglass boat deck, you should make it a habit.

Some boaters don’t know how often to clean their boat or why it is important in the first place.

To shed some light on the situation, I have answered a few of the most common questions related to boat cleaning.

Why should I clean my boat’s deck?

Just as one would think, a boat that is not cleaned will become dirty and loose value, pehaps even depreciating.

Our boats go through a lot of punishment from dirty shoes, weather, getting bashed, and a salt water environment. By cleaning your fiberglass deck you can help to ensure that it stays in peak condition.

How often should I clean my fiberglass deck?

Instead, ask yourself another question, “how often is my boat in the water?”

If you tend to keep your boat in the water 24/7, then you may want to clean the deck after every use.

In fact, you don’t need to use boat cleaner every single time. I’ve found that spraying it down after every use with a thorough cleaning once a week is ideal.

For those of us who keep our boats on land and occasionally take them out to see, the same rule applies. Giving them a spray down after a day of use will keep it from accumulating grime.

Since it isn’t constantly being exposed to water and salt, a thorough cleaning can happen less often, possibly every couple of months.

How do I clean the whole deck in one go?

Cleaning a boat can be really hard work, especially if you have neglected to do it or a long time.

I would recommend that you clean your fiberglass boat in smaller and more manageable sections.

How to remove oxidation from fiberglass boat?

Oxidation on fiberglass is a nasty business and can be tough to remove. To get rid of oxidization and deep scratches you can do a wet sand in really bad cases.

Most of the time though, you can just use a polishing compound such as the marine-grade ones on the market including Riptide or Crush liquid compounds.

Those products will remove oxidation from your fiberglass boat, and leave you with the gel coat and fiberglass looking as good as new. 

How do you remove wax from a fiberglass boat?

You should always wax your fiberglass boat before putting it into the water. It will give your gel coat a great looking finish and help to protect it. But, it will build up over time, and start to discolor.

Here’s how you remove the wax build-up:

  1. Soak a clean cloth with floor wax stripper.
  2. Mix a single cup of dish washer liquid to each gallon of water in a large bucket.
  3. Using circular motions, wipe the stripper on the cloth over the wax.
  4. Using a clean cloth, wash the stripper away using your water bucket mix.
  5. Wash down the boat with clean water once each area is complete. 

How do you remove leaf stains from fiberglass?

Use a waterline stain remover. This will take off the stubborn leaf stains away from the fiberglass without damaging it. 

The last word…

I’ve already mentioned how I don’t recommend using bleach to clean a fiberglass boat. And there’s a good reason why. 

There are lot of people who say you should, and plenty (me included) who say you shouldn’t.

I believe it will strip the wax on your deck and have seen small examples of that happening on my own boat.

Handy Hint: Are you looking to dispose of your old fiberglass boat? If so, read this guide which details various options you can use including recycling.

Yes, you can dilute the concentration down to make it is less harsh, but even so, keep in mind that bleach is not as environmentally friendly. It will harm the marine environment you boat in.

That’s why I recommend you should always use a liquid-based deck cleaner in substitution of a bleach product. You can read more here about why I don’t ever use bleach to clean my boat and deck.

Interestingly enough, if you compare the ingredients used in boat cleaners, they usually contain some concentration of bleach, it’s just not going to be as harsh.

This article was written by a contributor who owns a Catalina 22 fiberglass keel boat.