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Giant strides in inboards and I/Os

Technology in the diesel and gasoline inboard and inboard/outboard arenas really surged forward this year, with lighter, more efficient, quieter and cleaner power plants. Cummins, Mercury, Volvo Penta and Yanmar all have been touting new engines and/or drives at the fall boat shows.

GM Vortec 6.0L V-8 base engine

Mercury Marine now offers a 4.2-liter, 350-hp diesel, and Cummins has a new 6.7-liter diesel. Yanmar America’s the 370-hp 8LV diesel really tears up the water. Volvo Penta’s next generation of gasoline engines should do their fair of share of ripping, too. The company’s V8-380 gasoline sterndrive — introduced in September — improves acceleration and fuel economy in a package that’s lighter and more durable than its predecessor. “We did not stick with the same old, same old,” says Volvo Penta manager of engine engineering Mel Cahoon. “We didn’t just update what we already had. We chose to go forward. This is a new generation of our highest-horsepower sterndrive.”

The V8-380 uses the same engine that powers the Chevy Silverado 2500 pickup truck. Technological advances enable the V8-380 to generate the same horsepower as its predecessor — the 8.1-liter engine General Motors no longer manufactures — to more than make up for its lower displacement of 6 liters, or 364 cubic inches, says Cahoon.

The engine manufacturer in September also unveiled the V8-225 EVC, a 5.7-liter gasoline sterndrive that delivers power and torque and lower emissions through the use of computer-controlled fuel management and catalytic exhaust treatment systems. Both the 225 and 380 are Volvo Penta’s cleanest engines yet, satisfying California’s five-star emissions standards, says vice president of marine sales Marcia Kull.

Volvo Penta's V8-380 gas sterndrive

Volvo Penta gave the media an opportunity to demo the engines at a press event this past fall. A single V8-225 powered a Monterey 228Si, twin V8-380s powered a Formula 34 PC, and a single 380 was installed in a 260 Formula SS. I drove all three boats, and the acceleration was, indeed, impressive, especially in the midrange. The engines immediately responded to throttle adjustment. They also push their respective boats out of the hole with little strain. Pricing was unavailable.


The 370-hp diesel with ZT370 drive ranks as Yanmar’s highest-horsepower I/O package. The 8LV — a 4.5-liter twin turbo V-8 available in 320- or 370-hp configurations ­— can be linked to sterndrives or inboards.

I had a chance to demo the system in a 40-foot Nor-Tech center console at the 2012 Miami boat show. Like the Volvo Penta gasoline power plants, the Yanmar delivered bursts of speeds that snapped back my head. At 992 pounds, it weighs hundreds of pounds less than comparable engines and maintains Yanmar’s reputation for excellent horsepower-to-weight ratios, says Tom Watson, division manager of the Yanmar Marine Engine Division.

The 8LV delivers the fuel economy and durability for which diesels are known, with high-end performance similar to that of a V-8 gasoline model, says Watson. A hydraulic clutch ensures smooth operation, and the turbochargers help achieve an exceptionally broad 550- to 3,800-rpm power range. Yanmar’s CAN-bus vessel control system simplifies all controls, using full-color digital displays with NMEA2000 or J1939 output, cabling and wiring. Pricing was unavailable.


Cummins says its new QSB6.7 — a 6.7-liter diesel — packs more power and runs cleaner and more quietly than the 5.9-liter engine it replaces. It can be used for conventional inboard and Cummins Zeus pod installations.

The first Cummins engine to meet Tier 3 emissions standards, the QSB6.7 is about the same size as the QSB5.9, but it has a greater displacement and weighs 2 pounds less. The new power plant pushed a 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, according to Cummins. In addition, the QSB5.9 must work harder (3,400 rpm) than the QSB6.7 (3,300 rpm) to reach the maximum 480 hp. Also, cruising-speed engine noise levels are lower, the company says.

The engine can run on alternative fuels, such as kerosene, ultra-low-sulfur diesel and aviation fuel. The oil must be changed at 500 hours, compared with 250 hours for the QSB5.9. The QSB6.7 will be available in 380-, 425- and 480-hp ratings — the same as the QSB5.9. Pricing was unavailable.


The manufacturer’s 350-hp TDI 4.2-liter diesel debuted under the Cummins MerCruiser name but is now a Mercury Marine product. The engine gained some media exposure this past summer after Chris Fertig and crewmate Tyson Garvin broke the New York to Bermuda record in Fertig’s 37-foot Statement Marine center console, powered with a pair of the turbocharged direct injection diesels. They made the passage from the Statue of Liberty to St. George in 21 hours, 39 minutes. “The sterndrive diesel engines were extremely efficient,” says Fertig.

The 4.2-liter engines were linked to Bravo III XR drives. The engines operate efficiently, and tests show that the best mileage rating was 2 mpg at 33 knots, according to Steve Rock, category director of Mercury Diesel Engines and Commercial Markets. “When you think about a diesel engine, you think about an engine that is durable, but that is a tough concept to market, so this record helps show the reliability and durability … of the product,” says Rock. “From the perspective of a powerboat racer, efficiency equates to having to carry less fuel and running lighter and faster, while burning less fuel for a consumer means spending less money.”

In a joint venture, Volkswagen manufactures the V-8 engine for Mercury. In return, Volkswagen gets penetration into the U.S. market, says Mercury.

The engine can be installed in boats to 40 feet, including express cruisers and sportfishing boats, according to Mercury, and also can be a nice fit for large runabouts. Pricing was unavailable.

Volkswagen also manufactures and marinizes 1.9-, 2.5- and 3.0-liter diesels for Mercury at its plant in Salzgitter, Germany. The 1.9-liter is an inline 4-cylinder engine with a 40- to 75-hp rating. The 2.5-liter, an inline 5-cylinder engine, has a rating of 55 to 165 hp. The 3.0-liter V-6 is rated at 225 to 265 hp.

See related article:

- Joysticks everywhere

December 2012 issue