Preventing Mold & Fungus Tropical Boat Storage

[mightyhorton]

I'm closing up my boat and leaving it for a couple of months in Puerto Vallarta, and am worried about mold and fungus growing. The tropical monsoon rainy and windy season starts any day now, so leaving hatches or vents open, even under the boat's shade covers, could lead to a lot of rain getting in. Leaving a dehumidifier going could wind up flooding the boat if a drain clogged, or draining the batteries by overworking the bilge pump. I've heard that leaving open bags of charcoal, or placing pans of bleach water in several locations, inhibits mold, but these sound like old wives tales. Somebody suggested spraying a borate solution around on the inside closet walls, insides of cupboards, etc. Are there any generally accepted steps to be taken to prevent or inhibit the growth of mold? Thanks. Ian

[sailingdog]

There's is a new anti-mold/mildew prophylactic spray that was released about a year ago. It is supposed to be very good at treating hard surfaces, by spraying it on and letting it dry IIRC.

Ventilation is the key to keeping mold/mildew off the boat. Solar-powered vents are a very good idea, and the ones by Nicro are relatively water tight. A very large mesh bag of Calcium Chloride would also be a good idea.

Not a big fan of dehumidifiers, since they can cause more problems than they solve, especially if left unattended a long time.

Charcoal is a bad idea IMHO.

Originally Posted by mightyhorton

I'm closing up my boat and leaving it for a couple of months in Puerto Vallarta, and am worried about mold and fungus growing. The tropical monsoon rainy and windy season starts any day now, so leaving hatches or vents open, even under the boat's shade covers, could lead to a lot of rain getting in. Leaving a dehumidifier going could wind up flooding the boat if a drain clogged, or draining the batteries by overworking the bilge pump. I've heard that leaving open bags of charcoal, or placing pans of bleach water in several locations, inhibits mold, but these sound like old wives tales. Somebody suggested spraying a borate solution around on the inside closet walls, insides of cupboards, etc. Are there any generally accepted steps to be taken to prevent or inhibit the growth of mold? Thanks. Ian

[Vasco]

For the past four years I've been using Sun-paks when I store my boat They are bags of formaldehyde. Nothing lives on the boat including mold!! I hang about 7 throughout the boat including the lockers. You used to be able to buy them in Walgreens but they don't stock them anymore so I get them online. Just air the boat out after storage. Works like a charm.

[sailingdog]

While Formaldehyde should work quite well, be aware that it is a suspected carcinogen and rather nasty to deal with. From the Wikipedia entry:

Occupational exposure to formaldehyde by inhalation is mainly from three types of sources: thermal or chemical decomposition of formaldehyde-based resins, formaldehyde emission from aqueous solutions (for example, embalming fluids), and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases).

Formaldehyde can be toxic, allergenic, and carcinogenic.^[7] Because formaldehyde resins are used in many construction materials it is one of the more common indoor air pollutants.^[8] At concentrations above 0.1 ppm in air formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes. Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, as well as triggering or aggravating asthma symptoms.^[9]

Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency. The International Agency for Research on Cancer (IARC) has determined that there is "sufficient evidence" that occupational exposure to formaldehyde causes nasopharyngeal cancer in humans. ^[10] The United States Environmental Protection Agency USEPA allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency.^[11]


Formaldehyde can cause allergies and is part of the standard patch test series. People with formaldehyde allergy are advised to avoid formaldehyde releasers as well (e.g., Quaternium-15, imidazolidinyl urea, and diazolidinyl urea).^[12] Formaldehyde has been banned in cosmetics in both Sweden and Japan.

Not a particularly good option if you happen to be allergic or sensitive to it.

[Vasco]

Many folks who store their boats in FL use it. It comes in small bags in foil packs. Open and hang up. The formaldehyde turns to gas slowly. It's all gone when we return to the boat after six months but we do air it out. I think the epa warnings are why Walgreens no longer carries it. It's used extensively in FL to freshen bed linen etc.. Just put it in a large plastic bag for 24 hours. Very inexpensive too.