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How to Prevent Mildew on Boat Seats? – 2 Methods

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

how to prevent mildew on boat seats

Mold and mildew, in all their ghastliness, can ruffle any boat owner’s feathers. Every time folks ask me how to prevent mildew on boat seats, I always say you need to learn how to remove them as well.

Unless you lucked out and got OEM vinyl that’s immune to mold growth, you can only keep them under control for long, especially after storage.

This guide will be giving you invaluable pointers on how to remove mildew from boat seats and share what works best for me and other boaters in keeping its presence minimal, if not totally absent.

Prepare These Tools


If you want to go the all-natural route when cleaning mold off fiberglass boats, here’s what you need to prepare:

  • White vinegar
  • Borax
  • Warm water
  • Mixing bowl
  • Spray bottle
  • Scrub brush or sponge
  • N-95 mask and gloves

Should you decide to get mildew off boat seats using chemicals, here’s what I recommend:

  1. Star Brite or RMR-86’s mold and mildew remover
  2. Concrobium Mold Control
  3. PPEs

Proven Ways to Remove Mold and Mildew on Boat Seats and Shield Them Against New Growth

It’s time to remove mold and mildew! But first, put on the mask and gloves!

1. Natural Remedies for Mildew on Boat Seats

 01 With Borax Only


    1. Combine 1 cup of borax with a gallon of warm water.
    2. Soak the brush or sponge in the solution. Otherwise, you can just put the entire mixture into a sprayer. Remember to perform a spot test first!
    3. Wipe or spray the black spots on the boat seats. Let the solution stay on the surface you applied it to for at least 20 minutes.
    4. It should start to eradicate growth. If not, wait a few more hours.
    5. Once it’s all gone, rinse it then allow the seats to air dry.
 02 With Vinegar Only or Mixed with Borax


Should you decide to use only vinegar, it’s a matter of either mixing it with water or using it straight up. A caveat, though: cleaning with vinegar may damage the vinyl and its threads.

I’ve found that using a 1:1 ratio of vinegar and water works. However, since you’re aiming for boat mold prevention, then you can try using vinegar only. The idea is that the super low ph creates an environment where mold can’t come back.

I stress the importance of spot testing or contacting the seat’s manufacturer to confirm first, though.

If you’re going to mix with borax, just combine 2 cups of hot water with 1 tsp of borax and 3 tbsp of vinegar. Apply this homemade mildew remover similar to the first method.

2. Boat Seat Protection Products


The Chemical Stain Remover + Concrobium Strategy

As boat owners, we all want to keep mold off boat seats, and ultimately, the best way will always be to rely on chemical removers. These products come ready-t0-use, so you won’t have to do a lot of prep work. You just need to apply them properly!

  1. If you’re unfamiliar with how to use Star Brite or RMR-86’s mold & mildew removers, just purchase either one and follow the directions of use.
  2. Once you kill the mold (which has always been the case for me), simply follow it up with Concrobium. Again, stick to the instructions.
  3. From here on, it’s only a matter of waiting for the Concrobium to dry.

The Concrobium is really the one that’s mainly responsible for keeping mold away from pontoon boat seats based on my experience and a few case studies I’ve read online. It creates an invisible barrier, essentially. The cherry on top is that it’s also environmentally friendly and non-toxic.

Now, you may ask, “Why not just use the Concrobium to clean vinyl boat seats of mildew and mold and keep them away?” I hate to say it but Concrobium is not your dream mold cure-all.

For one, it doesn’t remove mold stains, even after you’ve killed off what caused them. This is why it should always be partnered with the stain remover.

Additional Preventive Measures

Fundamentally, what is prevention all about? It’s about eliminating the root cause. What causes mildew? Moisture, particularly under the boat cover.

  • You can combat humidity and keep those areas dry by installing a box fan that runs on a timer on the boat’s deck. It’s really all about keeping those cushions moisture-free
  • You can also keep mold from the boat interior by letting sunlight in. This doesn’t necessarily mean that you should forgo covers altogether. Just use ones that encourage ventilation – good examples are covered with built-in flaps.
  • Don’t adopt a “set and forget” mindset once you store your boat for the winter or any other reason. You still have to make time to maintain i

What Causes Mildew on Boat Seats?


I’ve mentioned the two culprits already: moisture and humidity. Unfortunately, vinyl, a common seat material, is subject to both. Once the mold growth starts, it’ll, in turn, feed on specks of dust, dirt, and other organic matter on the seat’s surface.

The Impact of Mildew Growth on Boat Seats

Mildew and mold can have many negative impacts including:

  • Leaves those stains that are nothing short of an eyesore.
  • Damages the seats over time. Once their integrity has been compromised, they may no longer impart the comfort they once provided.
  • Exposes seated passengers to the odor and health dangers of mold.
  • Reduces the boat’s resale value.

Factors That Contribute to Mildew Buildup on Boat Seats

The following may encourage mildew to grow and build up on your boats:

  • Improper boat cleaning habits. If dirt and dust are a ubiquitous presence on your vessel, then you’re basically letting inviting mildew growth.
  • Letting moisture linger on vulnerable parts of your boat.
  • Not exposing your vessel to sunlight enough.

Cleaning Solutions for Mildew on Boat Seats

You don’t have to scour forums and social media to look for the best cleaning solutions. For most people, it’s right in front of them, as evidenced by the popularity of products like Star Brite Mildew Stain Remover and its Better Boat counterpart.

You can also can find the best option for cleaning mildew on your boat seat here.

Both are straightforward to use and are formulated to be friendly to vinyl and other boat seat materials. If you’re considering other alternatives, such as bleach, stop that thought now! It will kill the mildew, alright, but it will likely wreak havoc on your seats as well.

How to Properly Maintain Your Boat Seats


Here are experts’ advised practices to keep boat seats from mildewing and maintain their good condition:

  • Keep an eye on wear and tear.
  • Schedule your boat for regular cleaning. Take out salts and other debris and contaminants.
  • Don’t use harsh power washers when cleaning.
  • Apply UV protectant sprays on them after removing mold or general cleaning.
  • Use boat seat covers that encourage ventilation.
  • Store and winter-proof your boat properly.
  • Stay on top of the “food” of mold and mildew mentioned above. Wipe and clean them as soon as they rear their ugly heads to make conditions as unfriendly to mold growth as possible.

Helpful Tips/FAQs


How often should I clean my boat seats?

Once a month with a gentle cleaner like a mild soap and wet soft cloth will do for most upholstery.

Are natural remedies effective in preventing mildew buildup?

Based on first-hand experience and my own research, I can safely say that natural remedies like the one shared above are only good for removing mildew buildup but not for keeping it away.

What is the difference between mold and mildew?

Not all molds are mildew. How each one grows provides a good clue. Mildew grows in a flat pattern, whereas mold grows while forming multicellular filaments termed hyphae.

Moreover, mold and mildew “eat” organic matter like wood, paper, and fabric, especially in spots where there’s little to no ventilation. Mildew is a type of mold that prefers wet areas.


Overall, of all the myriad ways how to prevent mildew on boat seats that I’ve read about, the methods showcased here are the only ones that have consistently given me positive results. I’ll take that advantage every day over an issue as perennial in nature as this.

I especially recommend the RMR-86 remover + Concrobrium combo that can knock out those pesky stains and keep them away for as long as I’m dedicated to applying them and cleaning my vessel regularly.

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