S.O.S.: Polluting Boat Ahead

Over the past decade, new Environmental Protection Agency (EPA) emissions standards for marine engines have encouraged manufacturers to phase out dirty two-stroke engines in favor of the more environmentally friendly four-stroke. Four-stroke marine engines are more efficient, with less raw fuel spilling out of their tailpipes.

But with more than 17 million recreational boats trolling U.S. waterways—up more than a million from seven years ago, reports the National Marine Manufacturers Association—should we be worrying about emissions from a variety of boats contributing to global warming and local air pollution?

Canadian Monte Gisborne, inventor of the world’s first solar-powered recreational pontoon boat, has a solution. His eight-passenger boat, the Loon, has a 30-mile range through an onboard lead-acid battery pack and overhead solar array. A diehard advocate of alternative technology, Gisborne has also created zero-emission electric cars, scooters and even snowmobiles.

“The exhaust from a four-stroke engine still carries a harmful mix of chemicals and even more greenhouse gases per gallon burned,” Gisborne says. “Four-stroke engines aren’t much friendlier to the environment.” Studies have emphasized the cleanliness of four-strokes when compared to two-strokes, but no studies have been done to examine the effects of four-stroke engines on their own.

“Is proliferation of many new four-stroke engines a problem?” asks Glenn Miller, an environmental science professor at the University of Nevada who is studying the effects of four-stroke engines on Lake Tahoe. “I don’t know. No one seems to know.”

Four-stroke boat engines are not as efficient as their land-based cousins, says Miller. And while their airborne emissions are monitored, the impact of toxins on the underwater environment is not factored into EPA assessments which focus almost exclusively on human health issues.

This could lead to a variety of problems, says Dr. James T. Oris, a professor at Miami University who has studied the effects of marine emissions on aquatic life. “Each group [of combusted and non-combusted materials] may have their own separate effects,” he says. “For example, a large number of boats idling in a small area can emit enough carbon monoxide to cause oxygen problems in fish and other animals.”

Alternatives exist. Electric marine engines are available from a number of companies, including Briggs & Stratton and Ray Electric Outboards.

“The only viable and sustainable solution is electric propulsion,” Gisborne says.