When my wife and I found our latest boat, it had been sitting in a South Carolina marina for over four years – almost untouched. The holding tank was full, the plastic ports and windows leaked and the overhead hatches had broken hinges. You can imagine how it smelled inside. In a perfect example of the triumph of hope over experience, I bought it anyway.

Capt. Pauley

Capt'n Pauley writes a column about boat repair weekly at LakeExpo.com

The sources of the smells inside the boat were many and varied. Sewage had sat in the head hoses and the odor had permeated them. Some of the interior woodwork had rotted and there was mold and mildew everywhere.

Today she smells like as fresh as a spring thunderstorm. What did I do? Like most complex problems the solution consisted of many individual elements, each of which contributed to a sweet-smelling boat. In this article, I’ll cover some of those elements that I used. They may not all apply to your situation but, hopefully, you’ll find something useful.

Cleaning Up

Due in part to some rot areas and also a desire to refurbish and upgrade the boat, I ended up removing and replacing substantial areas of wood below decks. This included replacing two main bulkheads, the panels beneath the v-berth, settees and quarterberth and the overhead.

As I stripped these areas out to the bare fiberglass hull was exposed. These surfaces were scrubbed down with water and Simple Green cleaner. Once this had dried I wiped the surface with acetone and then applied at least two coats of a marine one-part polyurethane paint.

A slight digression here. Using acetone, bleach, paint and other such items below decks requires adequate ventilation. Luckily the v-berth in my boat has a 24” x 24” hatch. I added wooden brackets to the sides of a 20” box fan so it would fit the open hatch. I ran this fan on high speed with the companionway open whenever I was using any of these chemicals below. The flow of fresh air also helped to eliminate the odors.

There are some paints that claim they are especially designed for bilges and the like, but I didn’t notice any difference in composition. I used the standard topsides paint. Instead of the more common gray, I went with an off-white color to lighten up dark storage areas. The paint made the bare fiberglass look better but it also seemed to encapsulate any odors absorbed by the bare fiberglass.

As new wood went into the boat, it was epoxy coated. This provided two benefits: it sealed the wood from any water penetration and reduced the possibility of trapping future odors in the wood. Most plywood was covered in either veneer or laminate. Remaining woodwork was scrubbed down with a mild bleach solution to neutralize and destroy mold or mildew and destroy odors. All interior wood then received at least six coats of satin marine varnish.

Heady Problems

The head was another matter. I completely stripped out all the interior cabinetry, down to the bare walls. The holding tank in the v-berth was finally emptied and removed as part of the v-berth rebuild. The walls of the head compartment were covered with an old vinyl textured material. This was all stripped off and replaced with almond colored laminate, smooth and easy to keep clean.

Before replacing the cabinets in the head, I lined the hull in the storage areas with aromatic cedar. The cedar comes in 1/4” thick pieces about 3” wide and can be found in most home improvement stores. I left it unfinished so the cedar odor could escape. It imparts a great smell to the towels and washcloths stored in the compartments.

One of the main sources of odor aboard the boat were the head hoses. These were original to the boat and had the contents of the holding tank sitting in them for at least four years. This was undoubtedly my least favorite job aboard. I bought plenty of adult diapers and crammed them underneath every hose before removing the hoses.

I replaced all the head hoses with Sealand Technology hose. This premium white hose was rated the best hose in terms of resistance to odor permeation by a leading boat equipment test magazine. It isn’t cheap but this wasn’t a job I wanted to do again soon.

I’ve also been advised that wrapping the head hoses in Saran Wrap before installing also adds a layer of protection.

Up in the v-berth, the holding tank had been removed and the compartment scrubbed and painted as mentioned above. In a normal holding tank installation, the lower outlet hose is usually full of wastewater – inviting odor problems. To eliminate this I installed a PVC standpipe. I’ll cover this standpipe idea in another article.  You can also use sections of PVC pipe in your holding tank plumbing as long as you install flexible hose in key areas, to avoid fracturing the PVC.

A Breath of Fresh Air

It is also important to provide plenty of ventilation for the holding tank itself. The odor-producing bacteria are anaerobic, that is they thrive in environments with little oxygen. Most tank vents are 1/2” or 5/8”. Experts suggest two 1” vents, one on each side of the boat, are better. This was impossible to do on my boat, but I did place a tank vent filter in the vent line to reduce the odor.

The enemy of all odors is a good supply of fresh air. To provide more fresh air in the head, I added a 10” x 10” overhead hatch. The hatch opening faced aft, so the air would flow from the forward facing bow hatch out the aft facing head hatch. I also added two opening ports aft in the cabin, one in the galley and one in the nav station. I also added an opening port in the aft end of the quarterberth, opening into the cockpit.

The original dorade vents were too small and allowed water to drain into the cabin. I made new dorade boxes and went from 3” to 4” cowl vents. To help with air circulation, I also added five 12 volts fans, two in the v-berth, two in the main cabin and one in the quarterberth next to the new port.

Generating Good Smells

All these things helped clear up the odor problem aboard. However, one part of our solution did more, faster, than any other thing I did aboard. Early on in the restoration project, I obtained two air purifiers from Quantum Pure Aire in Rhode Island (http://www.quantumpureaire.com/index.php). These purifiers generate ozone, which then destroys the odor molecules themselves. The ozone doesn’t mask the odors it destroys them.

I did some research on ozone before getting the units and found some controversy about it. There were some reports that breathing ozone in concentration might not be a good idea. But there was overwhelming testimony that the things really worked. I installed a small unit in the head (Photo #1) and a large unit in the main cabin (Photo #2).

I ran these things whenever I wasn’t on the boat, turning them off while working aboard. The odors immediately began to decrease and the boat began smelling better. I kept the units running for over three years, through dust, painting and epoxying below. The ozone kept the odors at bay and the boat pleasant. The smell is reminiscent of a thunderstorm, as lightning also generates ozone. If you aren’t rebuilding the interior of your boat but do have something of an odor problem, I’d suggest trying one of these units. They’ll operate on 12 volts as well as 110-volt shore power.

Well, now you have a bag of tricks that may help you to control the odors aboard your boat. Not a popular subject but important to get the most enjoyment out of your boat.