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What's New in Marine Propulsion Technology

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Today’s Marine engine manufacturers are using new technology to keep pushing powerplants in cleaner, lighter, and more user-friendly directions.

The days are long past when engine manufacturers introduced two, three, or even four new models at a pop. Today the emphasis is on evolution and fine-tuning of existing engines—at least until the next new technology appears. The big news is in the gasoline inboard and stern drive sector where we’re beginning to see—finally—the appearance of variable valve timing (VVT), a proven technology that has been available in automotive engines for more than a decade, as well as in many outboards introduced over the last few years. VVT will make a real and palatable difference in your boating when it finally trickles down to mainstream models. Right behind it in the automotive sector, but probably years away from appearing in boats, is direct injection, which could prove to be a real game-changer in marine power, providing a quantum leap in efficiency that could lure a lot of boaters away from diesels. But for now, we must settle for what the marketplace grants us. So here’s what to look for in the coming season.

Caterpillar C8.7

Caterpillar C8.7

Earlier this year CAT ( announced what has proven to be one of the most interesting new diesel engines to appear in a long time. Designated the C8.7 and developed in partnership with Fiat Powertrain Technologies (FPA), the engine features both a belt-driven radial supercharger and an exhaust-driven turbocharger, combined with a proprietary common-rail fuel delivery system. At low speed the supercharger provides added boost to increase torque and improve planing performance. Once the turbocharger is providing sufficient boost, the supercharger automatically disengages via an electromagnetic clutch. The result, says CAT, is virtual elimination of turbo lag and significantly improved time to plane. With a displacement of 8.7 liters, the in-line six-cylinder C8.7 is rated at 650 horsepower and is being promoted as a perfect match for the pod drive CAT announced last year. This is the first of two engines coming out of the CAT-FPA partnership. Next up will be a 12.9-liter model rated at 1,000 horsepower and utilizing the same basic supercharger-turbocharger technology. Volvo Penta offered a similar system in the ’90s but discontinued it after a few years, in part because of the high sound levels generated by the supercharger. No word yet on how CAT-FPA is handling that issue.

Read more about the C8.7 here ➤

Mercury engine

Mercury Stern Drives and Outboard Technology

Like to put a little more speed in your boating without going whole-hog on a pair of full-blown race motors? You’ll be interested in the news out of Mercury Racing (, a division of Mercury Marine (, that recently introduced a 520-horsepower (at the crankshaft) stern-drive engine that it says “fits nicely in both value and performance between the MerCruiser 8.2L MAG HO and the Mercury Racing 525 EFI.” Naturally aspirated, the engine represents a nearly 100-horsepower increase over the 430-horsepower 8.2L MAG HO yet still requires only regular pump fuel. It can be mated to the Mercruiser Bravo One XR, Bravo One XR Master, or Bravo Three XR stern drives, and comes with a two-year limited warranty. 

The two newest Mercury outboards are the 250 and 300 Pro Four Strokes. Both are in-line sixes displacing 2.6 liters, and like the rest of the Verado line, are supercharged with charge-air cooling. Standard features include power steering and this unusual option: your choice of either a 5.44-inch or 4.8-inch gearcase. The former, derived from the latter, is aimed, says Mercury, at “saltwater offshore boats that are run more aggressively or in rough seas where the propellers frequently ventilate.”

Speaking of Verado, Mercury has now adapted its Axius joystick control system to outboard use. Available only on the 250- and 300-horsepower Verados, the system can coordinate the movements of two, three, or four engines, providing the same point-and-shoot maneuverability that pod- and stern-drive owners have been enjoying for years.

Volvo Penta engine

Volvo Penta Stern Drive and IPS Developments

Volvo Penta ( is the only engine manufacturer to introduce both new gasoline and diesel engine models for 2014, and both are significant. On the gasoline side, there is a new 430-horsepower (at the crankshaft) version of the familiar General Motors 6.0-liter V-8, which, like its 380-horsepower stablemate, employs variable valve timing (VVT)—long a standard feature of automobile engines—to improve efficiency and increase low-end torque. That provides an important advantage in getting boats on plane quickly. Available only mated to the company’s DuoProp stern drive, the engine uses a hydraulic “camshaft phaser” to alter what would otherwise be fixed opening and closing of the valves. Other features include a catalyzed exhaust system to lower emissions levels; 4G ECM, the newest electronic control module, which accommodates the catalytic converters’ oxygen sensors; and an integral oil cooler. Output, as measured at the propeller shaft, is 397 horsepower, and maximum engine speed is 6000 rpm.

On the diesel side, Volvo has introduced three versions of the D11 diesel inboard, the D11-625, D11-670, and D11-725 (shown), with crankshaft ratings of 607, 650, and 703 metric horsepower respectively. The 607- and 703-metric-horsepower versions can be mated to the IPS 3 pod drive, in which case they are designated IPS800 and IPS950. Regardless of the ratings, the three models are physically identical; horsepower variations are effected via modifications to Volvo’s proprietary electronic control system or EVC. All engines use the same 10.8-liter (661 cubic inch) in-line six-cylinder block, electronic unit injectors, and twin-entry turbochargers, which are said to increase low-end torque output.

Yamaha outboard engine

Yamaha Four-Cylinder Four-Stroke Outboards

Yamaha ( introduced three new in-line four-cylinder outboards, rated at 115, 150, and 200 horsepower. All focus on reducing weight and size while maximizing power output through the use of double overhead camshafts activating four valves per cylinder, variable valve timing, and specially tuned intake runners to increase low- and mid-range performance. The 150 and 200 have internal counter-rotating balance shafts for smoother operation. Each engine has a different displacement—2.8 liters for the 200, 2.7 liters for the 150, and 1.7 liters for the 155—but what Yamaha is emphasizing is that they all share a relatively compact size and exceptional weight-to-horsepower ratio. For instance, the long-shaft 200 weighs just 487 pounds for a ratio of 2.4 pounds per horsepower. All three engines are able to accommodate fuel containing up to 10 percent ethanol.

Lehr 9.9-horsepower Propane Outboard

Lehr 9.9-horsepower Propane Outboard

Looking for a way to reduce your carbon footprint? How about a propane outboard for your tender? According to Capt. Bernardo Jorge Herzer, CEO and founder of Lehr (, “Propane is the absolute best alternative fuel solution we’ve found so far.” Well, everyone knows propane burns cleaner than gasoline, but is a propane outboard really practical? The new 9.9-horsepower model, introduced this year, could win over a lot of skeptics. No conversion, it was designed and built to be powered by propane, a fuel that the company claims, works out to about the same cost per mile as gasoline. What’s different and better is the elimination of traditional gasoline-related headaches like winterizing, ethanol, hard cold starting (no choke), and no worries about fuel spills. It’s also the first outboard available with electric start that does not require an external battery (there’s one tucked beneath the cowling). All three Lehr propane models purportedly perform the same as comparable gasoline engines, and the 2.5- and 5-horsepower Lehrs can operate either off a small screw-on canister or a standalone 20- or 30-pound propane tank. The 9.9-horsepower model requires a separate tank, and a 20-pound container of propane will reportedly power it for five hours at full throttle or 14 hours at normal cruising speed. The engine carries a list price of about $3,200 with manual start, short shaft, and tiller. Electric start, remote steering, and a long shaft are all available options.

This article originally appeared in the November 2013 issue of Power & Motoryacht magazine.