Low Emission Four-Stroke Outboard Marine Engine Utilizing Catalyst Technology


This page updated January 20, 2009

Chair’s Air Pollution Seminar

Wednesday, March 17, 2010
1:30 pm - 3:30 pm, PDT
Sierra Hearing Room, Second Floor
1001 I Street, Sacramento

This event is being Webcast, click here to view
Webcast viewers: Please send your questions during broadcast to: sierrarm@calepa.ca.gov
Presentation is available at this link

 Low Emission Four-Stroke Outboard Marine Engine
Utilizing Catalyst Technology

Jeff Broman

Product Development and Engineering Group
Mercury Marine, Fond du Lac, Wisconsin


A conceptual project aimed at understanding the fundamental design considerations concerning the implementation of catalyst systems on outboard marine engines was carried out by Mercury Marine, with the support of the California Air Resources Board’s Innovative Clean Air Technologies (ICAT) program.  In order to keep a reasonable project scope, only electronic fuel injected four-stroke outboards were considered.  While they represent a significant portion of the total number of outboard engines sold in the United States, carbureted four-strokes and direct injected two-strokes pose their own sets of design constraints and were considered to be outside the scope of this study. 

The integration of catalyst systems on outboards is much more challenging than on other marine propulsion alternatives.  Sterndrive and inboard engines are horizontal crankshaft engine derivatives of an automotive counterpart.  Outboards on the other hand utilize a vertical crankshaft, open loop cooling, and consist almost entirely of components that were specifically designed for a marine outboard engine application. 

This presentation will show how Mercury Marine designed a catalyst system for two families of outboard engines utilizing state of the art processes and design analysis tools.  Prototypes of one of the designs were constructed and tested.  Results of that testing will be shown that highlight the potential to meet four-star emissions levels and the challenges that will face commercializing this technology.


Jeff Broman, is a development engineer in the Product Development and Engineering Group at Mercury Marine.  Mr. Broman’s work at Mercury Marine has focused on engine thermodynamics development, including combustion, gas exchange, emissions, and engine calibration on conventional two-stroke, direct injected 2-stroke, and naturally-aspirated and pressure-charged 4-stroke outboard engines.  Mr. Broman has a B.S. in Mechanical Engineering from the University of Wisconsin.



For information on this seminar please contact:
Steve Church at (916) 322-8280 or send email to: 
schurch@arb.ca.gov

For information on this Series please contact:
Peter Mathews at (916) 323-8711 or send email to:
pmathews@arb.ca.gov

For a complete listing of the ARB Chairman's Series and the related documentation for
each one of the series
please check this page 


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