3 Proven Ways to Remove Mildew From A Boat!

Remove Mildew From A Boat

If you own a boat, you know what a chore it can be to remove mildew from canvas and other surfaces like vinyl.

Moisture and dampness easily build up in marine environments, which can cause stubborn stains and damage to the stitching on your seats and cushions.

On my boat, I get a lot of mildew on the vinyl seats, even though they sit outside in the sun. For this reason, I have tried a few different methods for cleaning mildew from boat canvas and vinyl.

How To Clean Boat Canvas Mildew

So, how do you remove mildew from boat canvas? Most canvas boat upholstery and seat manufacturers suggest a bleach-water combination to remove mildew from your boat seats.

There are a lot of recommendations on the best water-to-bleach ratio. I’ve tested them all and have found this combination is the best way to get mildew off boat seats.

The Best Way To Get Mildew Off Boat Seats

In a bucket, mix a bleach solution of 1 cup bleach and a quarter cup mild detergent per gallon of water. Saturate the canvas with the soapy water cleaning solution for 15 minutes and then blot or wipe off the solution with a microfiber cloth. Then with clean water and let air dry. 

The Bleach Formula:
1 Cup Bleach 1/4 Cup Mild Soap 1 Gallon of Clean Water (I prefer warm water)

How Do I Remove Mildew From Boat Canvas Without Using Bleach?

There are two main ways to remove mildew from boat canvas without using bleach. The first formula uses borax, and the second uses vinegar to remove mildew from your boat’s canvas.

Formula Using Borax To Remove Mildew From Canvas

To remove mildew using the Borax formula, mix 1/2 cup of borax with 2 cups of water to create an effective mildew stain remover. I prefer to use warm water, but use what you have. Use a soft bristle brush that will not damage the fabric or a magic eraser sponge to clean the vinyl boat seats of any loose dirt, debris, or residue left behind by mold spores.

Gently scrub the borax mixture into the canvas and loosen up the mildew. Allow the formula to soak into the nooks and cracks so it can get deep into the fibers.

Then after the solution soaks on the canvas for at least 15 minutes or longer, rinse the canvas thoroughly to remove all of the borax mildew cleaners. If the mildew is still present, is may require a second treatment to fully remove the mildew.

The Borax Formula:
1/2 Cup Borax 2 Cups Water (I prefer warm water)

Formula Using White Vinegar To Remove Mildew From Canvas

People have been using white vinegar as a cleaner around the house for generations. If you are a boat owner, vinegar can be a helpful product to use to clean your boat, too, while avoiding the use of harsh chemicals like chlorine.

Vinegar has many uses. One of the most helpful is using vinegar to remove mildew from your boat. White vinegar is a good bleach-free mold cleaner if you do not want to use bleach to clean your boat canvas.

Mix up a solution that is 1/2 white vinegar and 1/2 water. The brand of vinegar does not matter, I buy the cheapest gallon of vinegar I can find.

The Vinegar Formula:
50% White Vinegar 50% Water

You can also use 100% white vinegar and forgo the water. I have been known to put the vinegar in a pump sprayer and soak down the canvas.

Scrub it on in a circular motion, let it sit for up to an hour, and try to keep it wet the whole time.

If it starts to dry, I will mist it with a garden hose to help keep the vinegar wet and on the mildew stains.

After it sits for that long, I use a soft brush to agitate the canvas and create many bubbles until the mildew comes off. Then I blast it with a ton of fresh water.

Will Vinegar Make The Canvas Smell After It Dries?

No, using white vinegar to clean mildew out of the canvas will not cause the canvas to smell like vinegar after you rinse and dry the canvas. Once the vinegar dries completely, you do not smell it at all.

If you are still concerned about it, add a little Woolite or other mild soap to the mix, as was mentioned earlier, to add a little fresh smell to the canvas. This is completely optional, though.

What if you do not want to mix up your own DIY solution for removing mildew?

Are There Store-Bought Products That Will Remove Mildew From A Boat?

Plenty of products on the market are designed to remove mildew from vinyl, canvas, and other materials on a boat.

While some of the products are just not that effective, I found that this product works the best for me. Amazon Link

I prefer to keep a spray bottle of this stuff on my boat at all times. If I see any mold, fungus, or mildew starting to form on any surface on the boat, I will spray it and let it soak for a few minutes. Then I use a small hand brush, and I give it a few passes with the brush. I rinse it well, so it does not sit there too long, and that usually is enough to take care of most mildew issues.

You can buy it in bigger gallon containers online, but I just keep buying the smaller 32-ounce spray bottles.

Every now and then, I end up breaking one of the spray bottles so I like just being able to grab another one and not having to deal with pouring the chemicals into another hand spray bottle. Obviously, that is just personal preference.


Mildew on a boat is a real pain and an eyesore for sure. We all take great pride in keeping our boats clean and looking their best.

When I use any of the methods listed above (especially the bleach formula), it amazes me that even what I thought was clean vinyl or canvas; still comes out looking better than before I used the solution to clean the boat.

Bonus Tip: Clean Your Boat Hull With Toilet Bowl Cleaner! Does It Actually Work?

FAQ: How to Remove Mildew From a Boat

What is mildew, and why is it a problem for boats?

Mildew is a type of fungus that thrives in damp and humid conditions. It appears as black or dark green patches on various surfaces. Boats are particularly susceptible to mildew growth due to their constant exposure to water and the presence of moisture in confined spaces. Besides being unsightly, mildew can cause unpleasant odors and potentially damage the boat’s surfaces and materials over time.

How can I prevent mildew from forming on my boat?

To prevent mildew growth, proper boat maintenance is essential. Ensure that the boat is thoroughly cleaned and dried after each use. Open up hatches and windows to allow proper ventilation, reducing moisture buildup. Use moisture-absorbing products or dehumidifiers in enclosed areas, and keep the boat dry and well-ventilated during storage periods.

How do I identify mildew on my boat?

Mildew appears as dark spots or patches on various surfaces such as seats, cushions, carpets, sails, and even the boat’s hull. It has a musty odor and feels slightly slimy or powdery to the touch. If you notice these signs, it’s likely mildew growth.

What are some DIY methods to remove mildew from a boat?

Several DIY methods can effectively remove mildew from your boat. These include using a mixture of vinegar and water, baking soda, hydrogen peroxide, or a diluted bleach solution. Be sure to follow proper safety precautions and test the cleaning solution on a small, inconspicuous area first to ensure it doesn’t damage the surface.

Are there any commercial mildew removers available for boats?

Yes, many commercial mildew removers are specifically formulated for boats and marine equipment. These products are designed to be safe on various boat materials and are often more potent than DIY solutions. When using commercial cleaners, always read and follow the instructions carefully.

How can I remove mildew from hard-to-reach areas on the boat?

For hard-to-reach areas, use a soft-bristled brush or an old toothbrush soaked in the cleaning solution to gently scrub the mildew away. Take care not to scratch or damage the surfaces while cleaning.

Can mildew damage the boat’s upholstery and surfaces?

Yes, prolonged mildew growth can damage boat upholstery and surfaces. The fungus can break down and degrade materials over time, leading to discoloration, weakening, and foul smells.

How can I prevent mildew from coming back after cleaning?

After cleaning, ensure the boat is thoroughly dried, and maintain proper ventilation during storage. Consider using mildew-resistant treatments on surfaces, and periodically inspect and clean the boat to prevent any recurrence.

Is it possible to remove mildew stains from sails and canvas covers?

Yes, mildew stains on sails and canvas covers can be removed. Use appropriate cleaning solutions and follow the manufacturer’s instructions for the specific material. Be gentle while cleaning to avoid damaging the fabric.

Are there any eco-friendly options for removing mildew from a boat?

Yes, several eco-friendly options exist for mildew removal. Vinegar, baking soda, and hydrogen peroxide are natural alternatives to chemical cleaners. Additionally, using environmentally friendly mildew-resistant treatments can help prevent future growth without harming the environment.

Remember, tackling mildew promptly is crucial to prevent further damage to your boat and maintain its overall appearance and longevity.

Regular cleaning, ventilation, and proper boat care are essential in the fight against mildew growth.