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CMD engine an all-around upgrade

Cummins MerCruiser Diesel says its new 6.7-liter engine is more powerful, cleaner and quieter than the 5.9-liter model it replaces. The QSB6.7 — making its debut Feb. 16-20 at the Miami International Boat Show — can be used for conventional inboard and Zeus pod installations, says Jonathan James, CMD product manager for mid-range and heavy-duty diesels.

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The first CMD engine to meet Tier 3 emissions standards, the QSB6.7 is only an inch taller and 1.5 inches longer and wider than the QSB5.9, and it weighs 2 pounds less despite its greater displacement, James says. The 6-cylinder power plant packs more punch, too. The QSB 6.7 pushed CMD’s 44-foot Sea Ray test boat to 20 knots in 8 seconds; the boat takes 14 seconds to hit that speed with the QSB5.9.
“That’s a remarkable achievement,” James says, adding that the engine is used in the Dodge Ram pickup truck. In addition, noise levels at cruising speeds are lower, he says.
The QSB6.7 will be available in 380-, 425- and 480-hp ratings — the same as the QSB5.9. “We wanted to make it as easy as possible for boatbuilders to make the transition from the 5.9 to the 6.7,” James says.
Another positive: The 480-hp version doesn’t have to work as hard as the QSB5.9 to attain maximum horsepower, he says. “The 6.7 reaches 480 hp at 3,300 rpm, while the 5.9 gets there at 3,400 rpm.”
The engine can run on alternative fuels, such as kerosene, ultra-low-sulfur diesel and aviation fuel, and it requires an oil change after 500 hours, compared with 250 hours for the QSB5.9. Pricing was unavailable at press time.
Contact: Cummins MerCruiser Diesel, (843) 740-2726.

This article originally appeared in the March 2012 issue.