Complete Guide to Clean Fiberglass Boat


With the passage of time, your boat tends to get old whether you use it on a regular basis or not. And, as it takes ages to count, you feel the same shine is not there anymore.

Actually, you shouldn’t expect to, unless you try your best to keep it clean for long. But, if you own a fiberglass boat and you really wanna make it look new again, I have got news for you.

It’s true that your boat will surely lose the gloss due to exposure and time.

The outer gelcoat protection will wear away leaving it all gloomy and pale. But, it is also true that you can get the shine restored with a little effort.

How to Clean a Fiberglass Boat?

Generally speaking, there are multiple ways to do this. Let’s hit the easiest of ways, as I don’t want to tire you out already.

Again, we gotta work through it, okay?

Method of Clean a Fiberglass Boat

So, now we are gonna look at one method of getting stains off which is fairly simple. Although, you have to do it on a regular basis for expected results.

Use water solution to get it clean or bleach it to take off most of the normal stains. However, you will have to use something little bit more powerful to get the gelcoat stain out.

There are plenty of hull brightening products available on the market. You can use any of them to clean your boat.

Whatever the product name shows, it is usually hydrofluoric acid. You can cut that down to a mixture and use it in your sprayer to apply it.

As per my observations, hydrofluoric acid seemed good enough as it got the stains out in most cases. Plus, it didn’t cause any kind of oxidation around my stainless steel.

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Interestingly, today I’m talking about a stronger acid to use. It is erratic acid, the hydrochloric form of a strong acid.

It does the same job for you, but you will have to additionally make sure getting it off (don’t worry, you can just rinse it off at the end).

Since it is a stronger acid, we can’t risk the discoloration to take place around a stainless steel.

Tip: Both of the acids mentioned are hazardous. Please, exercise proper caution with protective gears.

Rubber or vinyl gloves up your sleeve, safety glasses are strictly suggested. Also, the cleaning must go in a well-ventilated area.

So now, you will have to pour in the acid into your sprayer. Mix around 20% of acid to 80% of water in your sprayer tank. In other words, you can say one part acid to four parts of water.

Leave a little bit of airspace in the bottle when you fill the rest of it with water. This will help the sprayer to pump up and work as it is supposed to.

These sprays minimize your contact with the chemical whether it is a bug spray or in our case; acid.

So, I discourage using hand sprays or hand application just to save around 15 bucks. Safety cannot be compromised.

Put the cap back at its place firm.

Then start pumping it up the sprayer and keep applying on the hull. Give it some time and observe the effects. You’ll notice a slight change in a couple of minutes.

Spray on the rest of the hull from top to bottom. You can also spray some on the floor if the floor got dispelled too.

You will have some of the yellows coming off soon as you finish applying the solution all over the hull. You can hit multiple applications till you get satisfied results.

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Normally, it could take 2-4 applications to show great results. The yellow and brown discoloration will be gone at this stage.

You may still have some broth and stuff, which you can try brushing off.

So, this is how you can eradicate the discoloration on your fiberglass boat’s gelcoat with such little effort and cost.

Important Tip: The acid has some effect on aluminum parts, like clowning and winding it up.

So, if you have a galvanized trailer underneath while cleaning the boat, it can wash out the zinc protecting it from rust and corrosion.

Another Method of Removing Oxidation from Your Boat

When you get that chalky residue, you know you have oxidation on your fiberglass gelcoat.

Sadly, oxidation doesn’t wash off, regardless of how many times you wash it. So, you will have to use specialized products to get that oxidized chalky effect off.

Step 1 – Cleaning

This begins with a simple wash. Simply take a bucket of warm water and pour a cup of detergent.

Stir it well till the detergent dissolves into the water. Then, wash the fiberglass surface with a sponge. Don’t forget to put on rubber gloves to protect your hands.

Tip: If the hull has fungal spots on it, an additional cup of bleach will be enough. And, in case of hard to wash crusts, you better use fiberglass cleaning acids or any rust converter on them.

Once you finish washing the boat, rinse it with clean water. Spare some time to dry it off habitually. Just how we discussed it earlier in this article, remember?

Step 2 – Degreasing

Fiberglass gelcoat is porous by nature. So washing alone can’t eliminate oil and grease particles from it.

This is why, you have to apply degreasing compound all over the surface using a damp cloth. Then rub it off using a microfiber towel.

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Step 3 – Polishing

After removing the oils and impurities from the gelcoat, you are going to repeat that same step.

But, this time with a polishing compound. Put some on your damp polishing pad and start rubbing in.

Don’t be afraid to use too much, because you should really rub it in good. When finished, take your microfiber towel to rub it all off.

We’ve also reviewed some good quality boat polisher. Read this review if ever need to buy one.

Step 4 – Waxing

Once you have got all your polishing compound off, it is time to hit the paste wax. Use the same technique with this as well; get some on your pad and rub it in.

Now, the only difference between your wax and compound is you have to let the wax dry until there is a nice haze on it.

Soon as it’s hazed over, then you are just gonna rub it all off. All done!

You should be overwhelmed to see the results by now. Congrats on the factory shine again! And anyway, have a great day!

If you face any problem while cleaning fiberglass boat, then don’t hesitate to inform us.

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