Development and Demonstration of a Low-Emissions Four-Stroke Outboard Marine Engine Utilizing Catalyst Technology

This page updated April 20, 2007.

Mercury Marine

Development and Demonstration of a Low-Emissions
Four-Stroke Outboard Marine Engine Utilizing Catalyst Technology

Technology and Innovation
Mercury Marine will engineer, design and develop the first ever four-stroke outboard marine engine that utilizes closed-loop engine controls and catalytic converter technology. While these technologies are well known and understood in the automotive, off-road, and small engine fields, they have never been successfully employed in an outboard marine engine. The challenges are that outboard engines must run water cooled exhaust systems, packaging is difficult in an outboard engine, the exhaust system is water-cooled, water (e.g., from a lake) can travel up the exhaust system into the engine. Mercury Marine will evaluate these challenges, develop solutions, engineer the product and build functional prototypes.
Emission Benefit
California’s regulations require attaining “catalyst-level” emissions only for inboard and stern-drive marine engines (5 g/kW-hr starting in 2008). Current regulated levels for outboards for 2008 are 16 g/kW-hr.  Mercury Marine believes that the target for a catalyst equipped outboard should be 5 g/kW-hr, a 70 percent reduction from currently mandated levels. Attaining this target in this project will be a key enabler for the ARB to propose catalyst-level emissions rules for outboard emissions.
Project Description
Mercury Marine will take a disciplined, engineering approach to this project, starting with a full analysis of the requirements, challenges, expectations, and design considerations, and culminating in building the first, ever, four-stroke outboard engine utilizing catalysts and closed-loop engine controls. The process that Mercury will use to reach this goal is the same process Mercury uses to develop new products. This will not be a “cobbled-up” engine and it will be an engineering prototype that will be developed as a production intent design. Mercury will build the lowest emissions four-stroke outboard marine engine ever built.

Funding Source

Funding Amount





ICAT Funded Projects