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Outboard Marine Engines
Clean Burning Motors
From the 2008 triennial, boaters were asked about their boat's propulsion system.  The Marine Board has an interest here because of a 1996 Environmental Protection Agency mandate that the marine industry produce a new generation of clean-burning outboards.  The final provision of the mandate was phased in in 2006 - thus, motors that meet the EPA 2006 emission levels are said to be "2006 compliant."  This data helps determine how quickly Oregonians are meeting the goal of reducing emissions through a production-level phase-out of carbureted two-stroke engines.
And, due in part to the decline in small boat numbers, Oregon is doing well in converting to the new, clean-burning marine engines. 
The number of boats powered by inboard engines has remained remarkably stable over the last decade at between 61,300 and 62,900 boats.  These motors are exempt from the EPA's 2006 standards because of their inherently clean design.  About 62% of Oregon's registered boats used outboard motors in 2007.  Of that62%, 49% are low to zero emissions.  When ajusted for the actual number of outboards, we see an 18% decline in the number of higher emission outboards between 2004 and 2007, or about 12,400 units, and a 6,300 unit increase in the number of low to zero emission outboards.

Results from 2005 (Outboards, PWC Engines) Survey
As a part of the Marine Board's Triennial Survey, the Marine Board asked boaters about the motor configuration on their boat. When compared against a 2001 survey, we see a strong conversion to low pollution technologies. For example, the number of carbureted two stroke engines used as the primary- engine declined in those three years from 70 to 51 percent. The number of quiet, clean-burning four strokes used as the primary engine increased from 12 to 26 percent. New technology two-strokes increased from 6 to 9 percent. The trend is evident in secondary engines, too. The number of carbureted two-strokes declined from 52 percent in 2001 to 31 percent in 2004, while four-strokes increased from 23 to 30 percent. Electric motors also increased from 23 to 30 percent.
We should also note that the number of clean-burning inboard engines continues to increase each year. If we combine inboards, 2006-EPA-compliant outboards and electric motors, an estimated 77 percent of boats on Oregon 's waterways now produce low emissions. New boat registrations run about 14 percent annually, with roughly the same number apparently being retired. This helps account for the rapid conversion to a low emission fleet. Based on these numbers, and the fact that the number of registered boats in Oregon has been flat to declining since 1998, hydrocarbon emissions from boats appears to be steadily declining.
Combined with the Marine Board's aggressive sustainable boating education focusing on invasive species prevention, hydrocarbon emission reductions and improvements of general clean boating practices, motorboats continue to have a smaller footprint on the environment.
Clean Boating Graph  

The EPA Phase-In Explained
Who: Working cooperatively with the marine industry, the Environmental Protection Agency (EPA) is requiring a new generation of marine engines featuring cleaner technology and better engine performance.
What: The standard for new engines requires a 75 percent reduction in outboard and personal watercraft engine hydrocarbon emissions from 1996 levels by the year 2006.
When: The rule was finalized in October 1996 and will be phased in over a nine-year period. The first step of the phase-in occurred in 1998.
Why: Many smaller boats and personal watercraft are equipped with conventional, carbureted 2-stroke engines. These light weight engines are easy to maintain. However, they expel relatively large amounts of hydrocarbons into the air. Engine exhaust, mixed with nitrogen oxide and sunlight, can produce harmful smog. Conventional 2-stroke engines produce roughly 14 times as much ozone-forming pollution as 4-stroke engines. Older engines can also discharge unburned fuel with their exhaust fumes. While most of this evaporates quickly, some may linger in the water for a while. New technology engines leave our waters cleaner.