United States
   Environmental Protection
Office of Transportation
and Air Quality
July 2006
                   Marine Engine Manufacturer
                   Develops  Low Emission  Inboard
                   Marine Engines
                  Over the past several years, EPA, the marine industry, U.S. Coast
                  Guard, California Air Resources Board, Southwest Research Institute,
                  and others have worked on a series of development programs geared
                  toward emission-reducing technologies for gasoline-powered marine
                  engines. These programs have had promising results. Now, one
                  manufacturer, who participated in these programs, Indmar Marine
                  Engines, is selling inboard marine engines with catalytic exhaust
                  aftertreatment, which reduces emissions from these engines.
                  Exhaust emissions from marine engines contribute to pollution:
                  hydrocarbons, nitrogen oxides, carbon monoxide, and particulate
                  matter. These pollutants can cause a variety of serious health effects,
                  from respiratory problems to cancer. In order to protect public health
                  and the environment, the Clean Air Act directed EPA to take steps to
                  reduce these emissions.

                  In 1996, EPA published exhaust emission standards for outboard and
                  personal watercraft marine engines. These standards, phased in from
                  1998 to 2006, were largely based on engine technology and achieved
                  approximately a 75 percent reduction in ozone-forming gases from new

In 2001, the California Air Resources
Board adopted emission standards for
new sterndrive and inboard marine
engines that are expected to require use
of catalytic converters, beginning in

In 2002, EPA gave notice of its intent to
develop a proposal for further emission
reductions from marine engines.  This
notice included a discussion on the
potential emission benefits that can be
achieved through the use of catalytic
controls and the ongoing development
and testing of catalysts on sterndrive and
inboard marine engines. EPA is now in
the process of developing proposed new
emission regulations for gasoline-
powered marine engines.
Overview of Catalyst
Development Efforts
Over the past several years, EPA has
worked with the marine industry, U.S.
Coast Guard, California Air Resources
Board, Southwest Research Institute, and
others, including several marine engine
manufacturers on a series of develop-
ment and test programs for the use of
catalytic exhaust aftertreatment on stern-
drive/inboard (SD/I) marine engines.
These efforts include:

 Laboratory testing of six catalyst
  designs on a SD/I engine
 In-water testing of boat with
  catalysts over severe operation
  (fresh and salt water)
 Full useful life testing of 4 boats
  with catalysts in fresh water
 Ongoing testing of 3 boats with
  catalysts in salt water
Results from this testing suggest that
significant emission reductions can be
achieved from SD/I engines through the
use of catalysts. The fresh water durability
study has shown that these emission
reductions can be achieved over the
lifetime of the engine. We anticipate that
the salt water testing will show similar

This year, one of the manufacturers
involved in the catalyst test programs,
Indmar Marine Engines, successfully
completed their own catalyst develop-
ment and durability testing program in
parallel with the work listed above. Now,
Indmar Marine Engines is selling inboard
marine engines equipped with catalysts,
and they report excellent emission perfor-
mance without any loss in performance.
Their efforts will help promote this clean
emission technology, which is capable of
reducing smog -forming gases by more
than two-thirds and carbon monoxide by
more than half.
For More Information
You can access documents related to gas-
oline-powered marine engine standards
on EPA's Office of Transportation and Air
Quality web site at:

   www. epa.gov/otaq/marinesi. htm

You can also contact us at:

   Assessment and Standards Division
   2000 Traverwood Drive
   Ann Arbor, MI 48105
   Voice-mail: (734) 214-4636
   E-mail: asdinfo@epa.gov