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Taming Boat Odors

A few simple steps can keep that familiar musty boat smell at bay.

Air conditioning unit, head strainer and propeller shaft

Your AC unit, head, and prop shaft seal are prime locations for ­bad odors. (Photos: Thomas Schmidt)

For the past 30-plus years, we've been fighting the good fight against boat odors. After a lot of trial and error, we've built the know-how to prevent boat odors before they establish a beachhead in our boat. When we open the boat on Friday evening after it's been closed all week, we're no longer greeted with that funky boat smell that seems to consist of some combination of fuel, mold, and stale water.

Our advice is to start your search-and-destroy mission by making a list of all the places where moisture accumulates. Then develop a plan to deal with the odors originating from each area. Here are our four prevention methods, which we use before closing the boat up for the week:

  • Add a small amount (approximately 1/8-cup) of mild household disinfectant/cleaner, such as a shower cleaner, to all drains, sumps, and air conditioning condensate pans. If the refrigerator and freezer are turned off, give each compartment a quick spray of the cleaner. It's also a good idea to leave the door ajar.
  • Spray shower sump pumps and grates with the same cleaner.
  • Pour a half-cup of the disinfectant into the prop shaft stuffing box area so the disinfectant follows the same drainage path to the bilge that the stuffing box drips use.
  • Disinfect and clean the toilet bowl upper ring area to prevent seawater odors. For this we use an in-line filter purchased from West Marine. In the filter housing, instead of a filter cartridge, we place a non-bleach, "blue tablet" type of toilet-bowl treatment. It treats the water whenever the toilet is used, pumps the solution throughout the sanitation hoses, and keeps waste odors at bay all week.

On our boat, the bilge is the collection point for the refrigerator drains, the air conditioning condensate pan drain, and water that comes in through the stuffing box. The trick to really getting rid of boat odors is in adding an environmentally friendly disinfectant to areas under the stuffing box and air conditioning condensate pans. The disinfectants find their way to the main bilge, eliminating odors along the way. Now when we arrive on Friday, we find a boat smelling sweet and welcoming.

Where's That Odor Coming From?

  • Closed sink drains — heads & galley
  • Shower sumps and/or drains
  • Refrigeration & freezer drains
  • Refrigeration & freezer condenser condensate pans (if equipped)
  • A/C condenser condensate pans
  • Prop shaft stuffing box drip area
  • Toilet bowl upper ring area
  • Main bilge
  • Potable water tanks

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Charles Fort

Contributing Editor, BoatUS Magazine

Charles Fort is BoatUS Magazine's West Coast Editor. He often writes local news items for BoatUS Magazine's Waypoints column and contributes to Reports, in-depth tech features in every issue written to help readers avoid accidental damage to their boats. He is a member of the National Association of Marine Surveyors, he's on ABYC tech committees, and has a 100-ton U.S. Coast Guard license. He lives in California.