Smoke on the Water

Ask cottagers the last place they would choose to swim, and most will say the local marina, where motorboats leave shiny pools of oil on the water's surface and clouds of blue exhaust in the air. The old-style, two-stroke engines that power the vast majority of Canada's approximately three million watercraft are major environmental polluters, fouling the marine environment and spewing large amounts of pollution into the atmosphere each year.

Emissions from non-road sources, such as power boats, lawn and garden equipment, and construction vehicles, comprise approximately 20 per cent of all smog produced by mobile sources in Canada. Unlike cars, however, marine engines have never been subject to emissions regulations and, as a result, are considerably less clean and efficient. According to estimates, a 70-horsepower (hp) two-stroke outboard emits the same mass of hydrocarbon pollution in one hour as a new car does driving 8000 kilometres.

Light, relatively inexpensive, and long-lasting, two-stroke engines have remained essentially unchanged since the 1940s. What makes them so inefficient and dirty is that the exhaust ports in the cylinders remain open for a short period of time while a charge of fuel and air flow into the combustion chamber from the intake port. This design results in some fuel exiting the cylinder before the exhaust port closes. As a result, the engine exhausts, unburned, as much as 40 per cent of its fuel. Another problem with two-strokes is that they require a mixture of oil and gasoline—so some of the exhausted fuel is raw oil.

Although outboard motors exhaust their emissions into the water, recent studies of their impacts on lakes revealed that most hydrocarbon compounds in the water migrated into the air within six hours, and that samples taken about a metre below the surface showed no contamination. However, heavier hydrocarbons, such as oil and grease, remain on the surface for a longer period of time and may affect the health of microscopic organisms.

To get a clearer picture of the content of marine engine emissions, Environment Canada's Environmental Technology Centre (ETC) in Ottawa began testing outboard exhaust for total hydrocarbons, nitrogen oxides, carbon monoxide, carbon dioxide, oil and grease, and BTEX (benzene, toluene, ethylbenzene, (xylenes)—carcinogenic or mutagenic aromatic hydrocarbons formed through the combustion process.

ETC's tests showed that two-stroke outboards produce 12 times as much BTEX as four-strokes, and five times as much oil and grease. Further comparisons of the exhaust emissions from a light-duty van, a 9.9-hp two-stroke outboard and a 9.9-hp four-stroke outboard showed that the two-stroke produced 50 per cent more carbon monoxide than the four-stroke and nearly 60 times more than the van. The two-stroke also emitted 15 times more unburned hydrocarbons than the four-stroke, and nearly 125 times more than the van.

Comparisons such as these shed light on the disparity between the emissions from on-road vehicles and outboard engines. On-road vehicles have been subject to emissions standards in Canada since the mid-1970s, which led to more advanced emissions control technologies being developed and applied. A significant reduction in emissions from these engines has been the result.

To address the issue of air pollution from marine engines in the near-term, Environment Canada and the Canadian Marine Manufacturers Association (CMMA) announced a Memorandum of Understanding in January of this year to voluntarily introduce cleaner outboard engines and personal watercraft (PWC) into the Canadian marketplace.

Under the terms of the Memorandum, new outboards and PWCs sold in Canada beginning with model-year 2001 must comply with United States Environmental Protection Agency (EPA) emissions standards for marine spark-ignition engines, and must come with an emissions warranty. The U.S. federal emissions standards seek to reduce levels of hydrocarbon emissions from gasoline outboards and PWC engines by 75 per cent over pre-control levels. These rules, which establish increasingly stringent emissions standards, have been gradually phased in since 1998, and will be fully implemented by 2006.

According to the CMMA, the Memorandum will ensure that newer, more efficient technologies will make it to the Canadian market, and that Canada won't be a dumping ground for non-compliant, older technology that is not certified for sale in the United States or other countries with emissions regulations. Consumers will see a significant change in the product line-up as a result. This new generation of engines and watercraft will be not only cleaner, but also more efficient—thereby reducing the consumption of fossil fuels and the creation of greenhouse gases that contribute to climate change.

In order to meet the EPA regulations, most outboards of less than 150 hp will likely employ four-stroke technology in the future. In comparison to two-strokes of the same horsepower, four-strokes consume about 30 per cent less gasoline at full speed, and as much as 80 per cent less when idling. They also produce less than 20 per cent of the pollution, and run more smoothly and quietly.

The reason for the increased efficiency and lower emissions is that the intake valve on a four-stroke opens to admit the air-fuel mixture only after all the exhaust valve at the top of the cylinder has closed. Also, because the lubricating oil is contained in an isolated reservoir, similar to that in automobiles, the design prevents this oil from entering the air-fuel mixture. This, in turn, prevents oil from being exhausted into the environment.

Two-stroke outboards aren't out of the picture, however, as several two-stroke Direct Fuel Injection (DFI) systems have been developed that eliminate the emission of unburned fuel from the combustion process. DFIs use high-pressure pumps to blast precisely timed bursts of fuel directly into the engine's combustion chambers after the exhaust port is closed. More complex and costly than regular two-strokes, DFIs have been on the market for some four years, but have generally been limited to models over 100 hp and to larger, more cost-effective markets. Although the engines haven't been the subject of emissions testing at the ETC yet, manufacturers claim they meet the 75 per cent hydrocarbon reduction target, and are 35 per cent more fuel-efficient than their conventionally carbureted two-stroke predecessors.

Both four-strokes and DFIs are more expensive than old-style two-strokes, but savings in fuel costs mean that buyers will quickly recoup their investments. Manufacturers have also developed small catalytic converters for use on outboards that show emission reductions of 73 per cent in some cases. However, because of engineering challenges, these devices have not yet seen widespread application. Diesel outboards also show a great deal of potential in terms of reduced emissions and greater fuel economy, but represent a very tiny percentage of the total market at present due to their higher cost and the lack of filling stations.

Policy experts and scientists at Environment Canada are currently developing a vehicle, engine and fuel action plan to address air pollution from mobile sources as one of a number of steps toward improving air quality in Canada. This plan, which will include input from stakeholders, will identify emission control programs, including regulations, and will be implemented over the next 10 years. The Memorandum of Understanding on marine engines will not only help bring Canada's marine industry into step with the most progressive jurisdictions, but also prepare it for the possible introduction of more stringent control programs in the future.

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