Die Mold! Die! – Part 2

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“Keep Calm and Stay Dry!” – Wall Plaque

In the last post of Die Mold! Die! we discussed the importance of taking a survey of your boat surroundings and finding all the nooks and crannies that mold and mildew hang out. Its a pervasive fungus! Worse yet – on a boat it can be growing in completely unreachable and unseeable areas.

We also discussed the importance of knowing the relative humidity inside the boat.

So, its time to talk about next steps. Being the smart readers you are you probably have guessed what the next step is… you need to remove the humidity from your boat!

There is a lot to it though! If you don’t keep humidity from getting back onto your boat, and you don’t arrest the humidity inside, you will never be able to permanently fix your mold and mildew problems. Here is a list of things to get you started:

Stop Boat Leaks

You need to get all the leaks on the boat sealed… if your boat keeps leaking because it rains or when you are sailing, or you have a hose or a faucet leaking inside you boat, you are not going to keep humidity out for long. This is especially true in areas where there is not a lot of air flow behind bulkheads, behind teak stripping, in cabinets, under the sinks, etc.

Use an Air Conditioner in Summer

We have a household window AC unit but you may consider getting a commercial marine unit if you have the payola. Dedicated marine units have their merits but those units break down constantly unless the installation is bullet proof. Among reasons why is that marinas that are cheap enough for long-term living are often in areas with a high silt particulate. This particulate clogs the inlet filter and is a real pain to keep clean, especially in winter. When we are cruising we don’t use AC however destinations such as the Bahamas have exceptionally clean water and they would work really well in those marinas! Keep your eye out for a future post where we teach you how to build a lasting hatch hood for your window air conditioner for five dollars.

Dehumidify in Winter

In the winter the cold hull interacts with the moist air in the boat and condenses that humidity on the inside of the hull. This results in literal rivulets of water working down from the cabin top. Warm air can hold more of that moisture in suspension so you will need to heat the boat to keep the humidity in the right range. Otherwise, you can wake up with water dropping on your face because your warm breath hits the ceiling and condenses. Conversely if you do not heat the boat you can wake up with a bloody nose because the air is so dry! You don’t need to buy an expensive boat dehumidifier but if you are not using an air conditioner that can dehumidify it does help to have a compact dehumidifier unit. A unit that has an outlet that will drain directly into a sink is helpful.

Keep Air Circulating

It’s important to keep air moving, especially in those areas that are prone to stale air…like the back of bunks, in the head, and inside cabinets and cubbies. We prefer the cageless Caframo fans because they move lots of air and are easy to clean. The downside is that they do not articulate as much as others styles.

Remove Wet Items Immediately

If you recently got a rain storm and stuff got wet, or you have a leak, or you recently showered, or you cat took a dunk in the ocean…you need to get the wet items off the boat right way. Dry them outside the boat – do not be tempted to dry them inside. Of course its it is below freezing you may have no choice.

Don’t Bringing Wet Stuff Onboard

It makes little sense to keep bringing wet items onto your boat once you have removed all the wet stuff! We have a ‘Wet Locker’ but we never -ever- allow wet items into the cabin from outside. We hang them on hangers in the cockpit instead. Also, you need to dry your laundry thoroughly. I know, I know… most marina laundries suck. They either don’t dry well enough or they don’t dry at all. Do you best to make sure you are not putting even slightly damp laundry back on the boat. Do NOT dry laundry inside the boat unless you have no other choice. However, don’t stop there… don’t bring warm laundry on the boat  either – it can mold. Use ammonia in your laundry to kill any existing fungus. Clean shoes of fungus and damp (check out a future post on how to keep clothes and shoes from molding).

Keep Wet Areas Dry

There are areas of the boat that will be perpetually wet or damp. Wipe and dry the bilge, under sinks, in recesses, up under the gunwale, inside the fridge, chain locker, and the shower. I know this is a difficult one and it’s unlikely you would be able to get all the water out. However, if there is water sitting around it is going to grow mold and mildew. If you are showering on the boat, you need to wipe up the bulkheads and wipe down the sump area. Make sure most of the water goes out a drain or [if you are using disposable cloth] into a sealed garbage container. Sinks are less of an issue than the shower but if you have major problems it doesn’t hurt to dry the sink area every time you use it.


Cooking on the boat puts out a lot of moisture… and you should allow that moisture to get out. You can crack open a hatch or a porthole to let the steam rise out of the boat. Obviously, if it’s dripping wet outside you may be better off leaving the boat closed up. Also helpful is the use of a pressure cooker to prevent moisture build up.

Shammy Towels for Showering

Lisa and I use shammy towels for drying off after a shower (even though we do not shower inside the boat). A good shammy doesn’t get smelly. You can ring them off outside of the boat or after you are done using them so they don’t evaporate into the air. Less humidity means that there is a less of a chance of mold and mildew taking a foothold or spreading. Look out for a future post on how to keep shammies clean and fresh.

Now that you have stopped moisture getting on the boat and gotten all the moisture OUT of the boat… there is one more step to knocking out place places mold can grow and live before you are ready to kill that mold off once and for all. Next week, we will discuss this next step.

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