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Diesel Boats and Ships

Marine diesel engines used on a variety of different types of vessels ranging in size and application from small recreational runabouts to large ocean-going vessels are significant contributors to air pollution in many of our nation’s cities and coastal areas. Marine diesel engines produced today must meet emissions requirements, but the current standards are relatively modest and these engines continue to emit significant amounts of nitrogen oxides (NOx) and particulate matter (PM), both of which contribute to serious public health problems.

EPA is addressing emissions from marine engines in two ways, through their fuels and through their emission limits.

In May 2004, as part of the Clean Air Nonroad Diesel Rule, EPA finalized new requirements for nonroad diesel fuel that will decrease the allowable levels of sulfur in fuel used in marine vessels by 99 percent. These fuel improvements, which begin to take effect in 2007, will create immediate and significant environmental and public health benefits by reducing PM from new and existing engines.

In March 2008, EPA finalized a three part program that will dramatically reduce emissions from marine diesel engines below 30 liters per cylinder displacement. These include marine propulsion engines used on vessels from recreational and small fishing boats to towboats, tugboats and Great Lake freighters, and marine auxiliary engines ranging from small generator sets to large generator sets on ocean-going vessels. The rule will cut PM emission from these engines by as much as 90 percent and NOx emissions by as much as 80 percent when fully implemented.

The final rule includes the first-ever national emission standards for existing marine diesel engines, applying to engines larger than 600kW when they are remanufactured -- to take effect as soon as certified systems are available, as early as 2008. The rule also sets Tier 3 emissions standards for newly-built engines that will phase in beginning in 2009. Finally, the rule establishes Tier 4 standards for newly-built commercial marine diesel engines above 600kW, based on the application of high-efficiency catalytic aftertreatment technology, phasing in beginning in 2014.

Information is also available on Gasoline Boats and Personal Watercrafts and Ocean Going Vessels.

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Guidance and Publications

Paper copies of this study are available from the National Technical Information Service (NTIS) - Publication #PB-92-126960

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Related Links

For more information, please email EPA's Assessment and Standards Division (asdinfo@epa.gov) or call the Assessment and Standards Division voicemail at 734-214-4636.

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