Dealing with Mold and Mildew on a Boat

Here in the Florida Keys, this time of year seems to be the worst for mold and mildew aboard the boat. Days are warm but nights are cool. An almost-imperceptible layer of condensation gets on everything overnight, then turns to mold/mildew in the heat of the next day. So what to do about it?

I’ve never found a 100% surefire way to stop it when living aboard. Some things may slow the growth down, but I’ve never found a way to totally avoid it. The best thing you can do is improve ventilation: open hatches, use wind scoops and fans.

Depending on the surface, I do a number of different things:

For hard surfaces such as gelcoat or plastic bins, I clean with either white vinegar (I usually use it full strength but you can dilute it 50/50 with water) or borax (Amazon) in hot water (about ¼ cup borax in a quart of water). Wipe but don’t rinse – the drying vinegar or borax will repel further mold and mildew to some extent.

Fabric I wash with borax – in a machine if that’s possible, or just sponging it on and then letting it dry when an item can’t go in the washer (for example, part of our walls are fabric lined). As it dries, you’ll be surprised at how much of the black stains disappear.

I use Miracle Mist (available on Amazon if not at a store near you) on more deeply stained items. However, Miracle Mist is primarily bleach (although it has some other ingredients, so it works better than bleach alone) so test it first in a inconspicuous place to make sure it doesn’t leave it’s own white spots! Further, Miracle Mist won’t slow down mold or mildew, so after using it I either use borax or Concrobium (available on Amazon and most hardware stores and big box stores in the paint department) on the surface to help in the future. NEVER use vinegar on a surface after Miracle Mist as bleach and vinegar can make toxic chlorine gas.

Concrobium doesn’t clean mold and mildew stains, but it does help prevent them in the first place so I often use it after other cleaning. Some people use tea tree oil but I haven’t found it that effective – it may have to do with the weather in your area or even the particular surfaces in your boat.

Our boat has lots of textured surfaces that turn black down in the grooves. I find that putting my cleaning solution in a spray bottle and spraying the surface seems to do a better job than just wetting a rag and rubbing it over. I also use a fingernail brush as a mini scrub brush on these areas.

If you use Miracle Mist – which does the best job of getting nasty stains out – be sure to wear clothes that you don’t care about as you’ll almost certainly get some bleach stains on them. And if working overhead with any cleaner but especially Miracle Mist, wear good eye protection. Glasses alone are too small, you really should wear goggles.

Overall, the tropics are wonderful . . . but mold and mildew are more of a problem than in many other places!

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