Boat Exhaust And Water Pollution: What's The Real Damage?

Boat exhaust is a significant contributor to water pollution. While not all boat engines exhaust directly into the water, all boats with engines create exhaust and emissions. The two most common types of boat engines are wet exhaust and dry exhaust engines, with the former discharging gas, oil, and other pollutants directly into the water. This introduces harmful substances such as petroleum exhaust, carbon monoxide, and heavy metals into the water, leading to fish deaths and contamination of the entire body of water. In addition, boat maintenance and marina construction can also contribute to water pollution through the release of chemicals, paints, oils, and sanitary waste. With the growing popularity of recreational boating, it is crucial for boaters and marina managers to adopt practices that minimize their impact on the environment and reduce water pollution.

Wet exhaust systems

Wet exhaust is the process in which cooling water is injected into the exhaust line, reducing the temperature of the gas and the accompanying fumes. This process also transports raw water or seawater and protects the engine against water entry. The cooled water then goes into a muffler that is specifically engineered to attenuate the sound produced by the engine while balancing backpressure allowances.

Generator wet exhaust systems connect with the generator and can be installed below, at, or above the waterline. Centek Marine mufflers are manufactured using fiberglass-reinforced plastics, which do not corrode or deteriorate when exposed to gasoline or diesel fumes mixed with saltwater or freshwater.

Engine type and maintenance

The two most common types of boat engines are "wet exhaust" and "dry exhaust" engines. Wet exhaust engines discharge gas, oil, and other potential pollutants directly into the water. This type of engine uses raw water from its surroundings to keep the engine cool, which is then expelled through the exhaust. Dry exhaust engines, on the other hand, do not discharge directly into the water.

When selecting an engine, it is recommended to choose a four-stroke design over a two-stroke model. Two-stroke engines are less efficient at discharging unburned fuel, resulting in more pollution in the water. Four-stroke engines can release up to 97% fewer pollutants, depending on the model. Additionally, the size of the engine should be considered, as larger engines may produce more pollutants.

To minimize water pollution, proper engine maintenance is crucial. This includes regular tuning to prevent fuel and lubricant leaks and improve fuel efficiency. Boat owners should also carefully fuel engines, recycle used oil, and properly dispose of worn motor parts. These practices not only help reduce water pollution but also contribute to the smooth operation of the boat.

Another aspect of engine maintenance is the use of antifouling paint. While it helps limit bottom growth, the chemicals and metals in this type of paint can be harmful to the environment. Therefore, it is important to select environmentally friendly alternatives whenever possible.

By following these engine maintenance guidelines, boat owners can play a crucial role in reducing water pollution and protecting the marine environment.

Sewage and sanitary waste

There are different types of MSDs, classified as Type I, Type II, or Type III. Type I and Type II MSDs are treatment devices that use chemicals to disinfect and deodorize sewage. However, it is important to note that many of these chemicals, such as chlorine compounds, formaldehyde, and ammonium compounds, can be harmful to aquatic life. Type III MSDs, on the other hand, are holding tanks that store treated or untreated sewage without discharging it overboard. These tanks may also incorporate technologies such as incineration, recirculation, and composting.

Federal law prohibits the discharge of untreated sewage in inland waters and within three miles of the shore. This includes sewage from portable toilets and Type III holding tanks. In some areas designated as "No Discharge Zones" (NDZs), the discharge of any sewage, treated or untreated, is strictly prohibited. Vessel operators in these zones must retain their sewage discharges on board for disposal at sea beyond three miles from shore or at onshore pump-out facilities.

To comply with regulations and minimize environmental impact, boaters should be aware of the type of sanitation system on their boat and follow proper procedures for its use and maintenance. This includes regularly emptying and cleaning holding tanks and, in the case of MSDs, ensuring that any chemicals used are safe for aquatic life. Additionally, boaters should familiarize themselves with the local regulations and restrictions for the waters they are navigating, as some areas may have more stringent requirements for sewage discharge.

By following these measures and staying informed about the potential impacts of sewage and sanitary waste on the environment, boaters can play a crucial role in protecting and preserving the health of our waterways.

Fuel spills and boating accidents

While fuel spills and boating accidents are rarer causes of water pollution than exhaust emissions, they can still cause massive destruction.

The Environmental Protection Agency (EPA) has implemented requirements that limit fuel vapor emissions and prevent fueling accidents. For example, most new boats with fixed fuel tanks include valves on tank vent hoses and fuel fills. When liquid fuel reaches the vent or the fill, those valves shut instantly, triggering the fuel nozzle to shut off. However, topping off after the tank is full can risk disgorging fuel and potentially damaging carbon canisters that scrub fumes from vent lines.

Fuel spills can occur at any time, especially during the fueling process at the fuel dock. To prevent spills, tools such as the FuelKleen collar by Centek Industries and the Clean Way Fuel Fill from Scandvik are available. These products surround the fuel nozzle with absorbent materials and seal it to prevent fuel from reaching the water.

If a spill occurs, it is important to identify the cause and source and stop the source immediately. Absorbent pads and booms can be used to contain and collect the spilled fuel or oil. In the case of a large spill, a vacuum truck may be required to skim the oil from the water's surface. It is illegal and detrimental to use soaps or detergents on a spill, as they allow the oil to disperse throughout the water column, making it harder to remove and contaminating sediment and more organisms.

Boat cleaners and paints

Boat owners often go to great lengths to keep their vessels in top condition, and the market for boat paints and cleaning products is extensive. Marine paints and coatings are designed to keep boats looking clean and new, while also protecting them from harsh weather and fouling creatures.

Boat paints include antifouling paints, which are designed to prevent the growth of aquatic organisms on the hull that can slow the boat down and cause damage. Antifouling paints are available in a range of types, including hard bottom paint, water-based bottom paint, and self-polishing-ablative bottom paint.

Boat deck paints are another important category, as decks can become slippery and dangerous. Anti-slip deck paints are designed to provide a safe surface for those working or providing activities on boat decks. These paints are available in a range of colours to suit the boat owner's preferences.

In addition to paints, there is a wide range of cleaning products available for boats. These include metal cleaners, waxes, restorers, polishes, and rubbing compounds. Solvents are also commonly used for paint application, thinning, and cleaning. For example, Interlux Fiberglass Solvent Wash 202 removes mould, release agents, wax, oil, and grease from the hulls of bare fibreglass boats. Other solvents used for cleaning include acetone, denatured alcohol, and toluene.

Boat owners can also purchase specialised products like propeller and running gear coatings, such as Propspeed and PropGlide.

Frequently asked questions