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Sourcing and Removing Nasty Boat Odors


Bill Ludlum asked:

We have a nasty odor inside the boat.
I have checked the holding tank (there is no leak), the head is working fine and the bilge is mostly dry.
Do you have any ideas or suggestions?

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Eliminating boat odors can be a frustrating exercise, especially if you don’t know where they are coming from. Worst, if not rectified fairly quickly, the smells can permeate the upholstery and wood inside the boat and remain for long periods of time. If you can’t identify the source then the answer is to over compensate. Attack all the possible odor sources!

The most common sources are the head, sanitation hoses, holding tank and bilge but they can also come from ice boxes, refrigerators and cupboards. Food that has slipped behind a cupboard drawer and is fermenting can smell up a boat as much as the head.

Start with the sanitation system. Before you start, pump out the holding tank and treat the system with 8 or 10 ounces of Odor Free, pumped from the head into the tank. Give it a day or two to work. This may not solve your problem but it will make further inspection less offensive. It’s never pleasant.

Next, make sure that the vent hose is not blocked. First check that the exterior vent is not blocked. Dirt, excessive wax or polish even a spider nest can cause this to be inoperable, forcing the odor from the tank, back into the boat every time you flush. It’s also possible that sludge or an accumulation of toilet tissue could block the vent at the tank. If the exterior vent is clear, disconnect the hose at the tank fitting and make sure that it’s not blocked there. If you have a compressor, try blowing air through the hose. If it’s blocked then replacement is in order. Make sure that all hoses are double clamped.

Inspect the sanitation and pump out hoses and give them a squeeze. (Wear rubber gloves) If they are soft and spongy you will have to replace these hoses. Use a clean dry cloth and give these hoses a wipe. Smell the cloth. If it smells, you have a problem with permeation odor from the hose. This is common when bleach, the wrong toilet chemical or no chemical at all is used. It this is the problem and the hoses are still in good order, Odor Free can often eliminate this smell. Try flushing one or two ounces of Odor Free through the hose on a daily basis. Fill the bowl with water, pour the Odor Free into the bowl and give it time to dissolve, then flush it through. This may take a week or two but it is very effective and has saved many boat owners from having to replace the sanitation hose. If it’s the pump out hose, dissolve one or two ounces in a gallon of water and pour it into the pump out fitting.

Another problem with holding tanks is sludge build up. Again this can happen when the sanitation system is not properly maintained or the wrong chemicals used. Odor Free will break up the sludge and digest toilet tissue over time so it can be pumped out. In time, your tank will be clean and this source of odor will be eliminated. Regular use of Odor Free in future will prevent these types of odors from returning.

Freshening bilges can be tricky. On most modern boats the bilge is not completely accessible. Bulk heads and stringers are often covered by the sole or floor of the boat and the only access is through limber holes in the stringers, designed to let water drain over the length of the boat. Even though the bilge is mostly dry, it’s possible that some water made its way into the bilge or there could have been grease, oil, diesel or gasoline dripped into the bilge at some time. This combination will result in sludge building up on the inside of the hull which can foster mold and mildew growth. To clean and freshen the bilge, pour Bilge Bath into the bilge along with a bucket or two of water. Take the boat out and let the mixture slosh around. Bilge Bath will loosen and wash sludge, mold and mildew from the bilge and the odor counteractant “Odolime” will knock out the smells, even of diesel and gasoline. When back at dock, pump out the liquid for disposal on shore. Bilge Bath is biodegradable, but some of the stuff that it looses may not be.

Wash the refrigerator, ice boxes, livewells and the inside of the cupboards with Boat Clean Plus and rinse with water. Pull all the drawers out and inspect behind and below them for any refuse or dead rodents.

The upholstery and carpets can be shampooed with Boat Clean Plus. Pour some into a bucket and use a sponge to create foam by squeezing and releasing several times. Use a sponge or brush to work the foam into the fabric and then use a wet/dry vacuum to suck up the moisture and let it dry. The walls and bulkheads can also be washed with Boat Clean Plus and water. Make sure that the surfaces are color fast before washing. Most headliner materials can also be cleaned this way.

The only other possible remaining source of odor is from the engine. If it’s greasy, it can be washed with Boat Clean Plus or Bilge Bath. After cleaning wipe the engine with a light oil on a clean cloth to prevent corrosion. If you have an exhaust leak or blow by then get your mechanic to address these issues. Breathing engine exhaust from exhaust leaks can present a health hazard and can even be fatal. They need to be treated immediately and seriously. Don’t use your boat if you have exhaust fumes in the boat.

I suggest following these procedures in order until you have the problem solved.

Thanks for your question,
Captain Aurora

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