| Marine Engine Catalytic Converters | | Print | |
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MerCruiser and Volvo Penta now produce engines with catalytic converters. Here’s how they pulled it off. Originally published in December 2008 issue By Matt Trulio Greatly simplified, a catalytic converter uses extreme heat to reduce an engine’s emissions of hydrocarbons and carbon monoxide. The proven technology has been standard fare on automobile engines for decades, but on the marine side—at least in the pleasure-boat market—catalyst-equipped engines only arrived on the scene this year. That’s because the California Air Resources Board mandated that, in January 2008, all marine engines of 500 horsepower and less sold in the Golden State had to be equipped with catalytic converters. And by 2010, thanks to an Environmental Protection Agency mandate, all marine engines in the 500-hp-and-under class sold in this country will have catalyst systems. 
So why did it take so long for this environmentally friendly existing technology to be embraced by the marine industry? There are a number of reasons, but perhaps the most compelling was the justifiable concern over putting something so hot—catalysts can reach 1,000 degrees—in a fiberglass engine compartment. Another concern centered on a catalytic converter’s ability to survive in a marine environment, particularly in the saltwater realm. To find out how the two leading marine engine manufacturers in the country pulled it off, we talked to Robert Grantham of MerCruiser and Paul Dierksen of Volvo Penta of the Americas. Both declined to describe their proprietary technologies in specific detail, but did provide a general overview of the development process and challenges. Grantham said the biggest hurdle was designing for full catalyst functionality in an engine compartment that, because of the catalyst, required a water-cooled exhaust system to maintain low external component temperatures. Other considerations included keeping costs down, maintaining performance and reliability, and packaging within the typically limited confines of a boat’s engine compartment. He said engineers at the company started working on its catalyst technology more than a decade ago. “It took careful and creative design that respected the space constraints while allowing the catalyst to operate at high temperatures while maintaining low external temperatures,” Grantham said. “This was accomplished by providing an air gap between the catalyst and the casting, and then creating a cast water-jacketing outer surface. “We paid close attention to cost and the judicious use of precious metals necessary for the manufacturing of the system,” he added. “Unfortunately, the marine requirements differ enough from the automotive industry that it was not feasible to simply ‘borrow’ directly from current automotive parts bins.” All of MerCruiser’s gasoline multi-port fuel-injected models are available with catalytic converters, including the new 3.0 MPI, which is only available as an Emissions Control (EC) model. This engine remains rated at 135 horsepower like its TKS carbureted cousin, and all other engines retain their non-EC horsepower rating as well. MerCruiser offers EC engines in stern-drive and inboard configurations up to the 496 Mag HO, which is rated at 425 hp. The engineers at Volvo Penta faced all of the same constraints. Not increasing the “envelope size of the engine” for boatbuilders, said Dierksen, was paramount. Also crucial was maintaining the power output of each engine, not significantly increasing weight and making sure the catalyst would last through the warranty period and beyond. “We were fortunate in that the water-jacketed manifold fit the envelope we currently have,” Dierksen said. “We overcame the weight issue by developing an aluminum manifold, which is a little lighter than our previous manifolds. The aluminum water-jacketed manifold overcame the heat and weight issues. “Our engineers did an exceptional job with that,” Dierksen added. “They also did an exceptional job with exhaust tuning and engine calibration to meet the emissions standards without losing performance. The consumer won’t notice a difference in performance—in our 8.1-liter engine we actually picked up a little horsepower. But consumers really won’t notice a difference between the (catalyst and noncatalyst) engines. And that’s as it should be.” Volvo Penta engines available with catalyst systems include the 3.0-liter, 5.0-liter, 5.7-liter, 8.0-liter and 8.1-liter models. Power ranges from 150 to 400 horsepower. —Matt Trulio is a freelance writer for Powerboat magazine. —Matt Trulio is a freelance writer for Powerboat magazine. If you like what you're reading, get more by subscribing to Powerboat magazine here. Contact Information Volvo Penta of the Americas, 1300 Volvo Penta Drive, Chesapeake, VA 23320, 757-436-2800, www.volvo/volvopenta.com |
