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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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Keep the gas in the tank, not in the water. This device is attached to the fuel pump. It absorbs the back flush when fuel is pumped, so it won't spill into the water. © Robert Queen
Keep the gas in the tank, not in the water. This device is attached to the fuel pump. It absorbs the back flush when fuel is pumped, so it won't spill into the water. © Robert Queen

August 2002

On land and in water

How boaters can control pollution.

Natasha Kassulke

Sanding, blasting and painting
Waste | Sewage | Fueling | Engine

Boaters know how much work goes into keeping a boat clean and working well.

But many boaters are also learning that their choice of products and maintenance methods impacts water quality and aquatic life.

On land, and in the water, there are ways boaters can control and prevent pollution.


Working on a boat out of the water and on an impervious surface under cover will prevent stormwater from carrying pollutants into the water.

With large boats, and those moored in permanent locations, this may not be practical. In those cases much care must be taken to capture paint chips and other debris by working over a filter fabric or tarp. A berm or retaining wall may be built to capture debris.

Boats should be washed often with plain water and scrubbed using a sponge to prevent algae and other growth. Detergents should be phosphate-free, biodegradable and nontoxic. Even biodegradable detergents should be used sparingly, since some can destroy oils on fish gills and inhibit fishes' ability to breathe.

Likewise, teak should be cleaned with a mild soap and abrasive pads.

Instead of pressure washing, clean hulls above the waterline by hand to reduce the amount of water needed and the total contaminants entering the water.

If pressure washing is necessary to remove bottom growth, minimize impacts by using filtration or chemical treatments that settle out heavy metals and paint solids. If pressure washing, use the least amount of pressure necessary to remove the growth. A garden hose and soft cloth may be enough.

If underwater hull cleaning is necessary, make sure there are no colored plumes, which indicate paint is being removed. Use the least abrasive material practical (sponge or soft carpet) when cleaning a vessel in the water.

Sanding, blasting and painting

Vacuum sanders and grinders, which collect dust as soon as it is removed from the hull, may be bought or rented. Paints, thinners and solvents may be toxic, and fumes – volatile organic compounds (VOCs) – released by some paints and solvents pollute the air.

Select fast-drying, environmentally friendly bottom paints. Nontoxic coatings are the most environmentally friendly and contain Teflon or silicone to produce hard, slick surfaces that plants and other organisms cannot firmly attach to. Use water-based paints when practical. Share leftover paint and varnish.


In 1987 Congress passed the Marine Plastic Pollution Research and Control Act to regulate garbage disposal at sea. Under federal law, it is illegal to discharge plastic or garbage mixed with plastic into any waters.

Regional, state or local regulations also may apply. All garbage disposal is prohibited in the Great Lakes and connecting tributary waters. Violators face a civil penalty, a fine, and imprisonment.

When boating, use reusable containers and products with less packaging. Recycle as at home and properly dispose of all trash onshore. Trash should be taken home or left in the proper dumpster at the marina. Recycle used oil, oil filters and antifreeze. Used solvents and waste gasoline may be disposed of at a local hazardous waste collection station.

Find out what the marina's fish disposal policy is. Bag the waste and compost or dispose at home or in the proper dumpster.


"In Wisconsin, we don't allow any discharge of sewage treated or untreated into our waters for recreational boaters," explains James Lubner, an educational specialist at UW Sea Grant Institute in Milwaukee.

Lubner explains that many people on small boats use portable toilets, which can be drained at toilet dump stations. However, vessels over 26 feet long typically have installed toilets.

The Clean Water Act requires that all vessels with installed toilets have a certified Type I, Type II, or Type III Marine Sanitation Device (MSD).

Type I systems mechanically cut solids and disinfect waste. Type II systems treat sewage to a higher standard and generally require more space and energy to run. Type III systems do not discharge sewage – holding tanks are common. Incinerating systems are another option.

Some marinas provide a sewage pumpout station.

"If there's a problem in freshwater that relates to sewage," Lubner contends, "it's probably due to a lack of easily available pumpout stations."


Several products prevent spills and reduce emissions when fueling. A fuel/air separator installed along the vent line allows air, but not fuel, to escape through the vent opening. A safety nozzle attached to a portable gas line used to fill outboard engines automatically stops the fuel flow when the tank is full.

A bilge switch may be installed to prevent oily bilge water from being discharged. Alternatively, a bilge water filter connected to the vessel's bilge pump filters oil, fuel and other petroleum hydrocarbons from the water.

When fueling, only fill the tank 90 percent to allow room for thermal expansion. Slow down at the beginning and end of fueling. Fill the tank just before leaving rather than returning from boating to reduce spillage due to thermal expansion.


EPA requires each outboard motor manufacturer to decrease overall emissions of its line by a certain percentage by 2006. New four-stroke motors meet these requirements and are why some boaters are switching over from two-stroke engines.

An EPA study shows that approximately 25 percent of the fuel/oil mixture from two-stroke engines are emitted unburned in exhaust. EPA data also shows that two-stroke engines produce over eight times the hydrocarbon emissions produced on average by four-strokes.

Four-stroke engines also are quieter, more fuel efficient and fowl fewer spark plugs than two-strokes. Four-stroke engine parts are lubricated without mixing oil and gasoline.

The downside to four-strokes is that they cost at least 10 to 15 percent more than two-strokes, and need periodic checking of crankcase oil level, and regular oil and filter changes. Larger repairs for four-stroke are generally more expensive and involved.

New direct fuel injection (DFI) two-strokes, while not as clean as four-strokes, produce significantly lower hydrocarbon discharges than other two-strokes. Using fuel injection and variable exhaust ports also reduces personal watercraft emissions by 75 percent.

Michael Moore, a biologist at the Woods Hole Oceanographic Institute in Massachusetts, points out that there are other sources that also leak fuel and hydrocarbons into the water – personal watercraft, leachate from paved roads, sump oils, carbon black from tires, fuel transfers, oil spills, leaking storage tanks and more.

No matter what kind of engine you have, ensure that it operates as effectively as possible and use the gas-to-oil ratio recommended by the engine manufacture.

There are two types of antifreeze on the market. Ethylene glycol, the traditional antifreeze often identified as green or blue, is toxic and should be collected and recycled. Propylene glycol antifreeze, the pink antifreeze, is less toxic, but is still harmful to the environment and should be recycled or disposed of properly.

Be a cautious consumer. Carefully read product labels. And pay attention to signage in and out of the water.

Natasha Kassulke is Associate Editor of Wisconsin Natural Resources magazine.