It’s hard to beat a clean sheet of paper—and that was the metaphorical starting point for the new MerCruiser 6.2L MPI, a V8 engine Mercury Marine is shipping for sterndrive and inboard applications. Rated at 300 or 350 horsepower in sterndrive and inboard trim, and 320 and 370 horsepower for inboard tow boat applications, this engine is an all-new design created expressly for marine use, executed in-house by Mercury, and exclusive to the company. In this regard, the new 6.2L MPI follows the path blazed by the MerCruiser 4.5L MPI, a 200 or 250-horsepower V6 introduced last year. In fact, according to David Foulkes, vice president of Mercury product development, the 4.5L and 6.2L share about 65 percent common parts.
At the recent media introduction of the MerCruiser 6.2L MPI, Foulkes repeated the assertion he made last year when Mercury launched the 4.5L engine—that Mercury sees little benefit for the marine industry in many current and emerging automotive engine designs. For generations the marine industry has relied on “marizined” versions of automobile engines, primarily sourced from GM Powertrain and Ford, for its gas inboard and sterndrive engines. Today fuel mileage is the primary focus of auto engine development, according to Foulkes (who is a former Ford powertrain chief engineer), even for the light trucks typically powered by the engines sourced for marine duty.
“New automobile engines are designed to work best at a very light load,” said Foulkes. “When you think about driving your car or truck, you spend most of the time at 10 to 15 percent throttle. A marine engine, by comparison, has to cruise at perhaps 75 percent throttle.”
While Foulkes recognizes the value of technologies like variable valve timing, all-alloy construction and direct fuel injection in the automotive arena, he feels that due to cost and complexity, those features are of little advantage in a boat. And the latest engines being offered by GM Powertrain, including its LV1 4.3-liter V6 and L83 5.3-liter V8, feature all of those technologies. Those GM engines are being marinized by Volvo Penta, the chief rival to Mercury in the sterndrive market.
And so, that clean sheet of paper, or rather a blank CAD screen, was the starting point for the MerCruiser 6.2L V8. Foulkes says that like the 4.5L V6, the new 6.2L is based on an iron block cast to Mercury specifications.
“The V8 is the same premise as the V6,” says Foulkes. “We started with sufficient displacement and then designed an engine with a focus on eliminating the friction that results in parasitic power loss. We selected light-weight connecting rods and pistons, fitted low-drag piston rings, limited oil drag on the crankshaft, and because we are designing our own engine, were able to manage details like selecting the optimal bearing sizes.”
Components that come in contact with raw water—the engine block, cylinder heads and exhaust—are cast iron. All other components are aluminum or composite, according to Mercury. The engine will be offered with either raw water (open) or freshwater (closed) cooling. The 6.2L engine weighs 862 pounds, or about 23 pounds less than the 6.2-liter MerCruiser 377 MAG engine it will replace.
A key feature is the design of the long-runner scrolled intake manifold, which boosts torque by packing more air into the combustion chambers. The throttle body opening faces aft so that intake noise is not aimed directly at the cockpit. On marinized auto engines the intake faces forward, because the engine was originally designed for a truck. To further suppress intake noise, Mercury has for the first time designed a resonator that fits between the throttle body and the flame arrestor. I’ve been waiting years for Mercury to design this feature because I’ve seen its state-of-the-art sound lab, which is staffed by PhD engineers who spend a lot of time tuning the intake of Mercury outboards. In the past I’ve been told that it was not possible to design an inboard intake resonator that was compatible with U.S. Coast Guard flame-arrestor regulations, but apparently Mercury has figured that out. Mercury also designed the 6.2L to limit vibration, and large engine mounts help isolate the engine from the boat.
As it did with the 4.5L V6, Mercury has placed all common service points on the front of the 6.2L engine, including the engine oil dipstick, the oil filter, the oil fill point, the power steering pump and the outdrive lubricant reservoir. Most service specs are printed on a label on the front engine cover, and there’s a scan-able QR code for links to DIY service videos. For a first-hand look, click on the picture to see a quick video.
The 6.2L V8 will be offered with a choice of Mercury SmartCraft DTS digital or analog controls, with joystick piloting available with DTS. The 6.2L also features Adaptive Speed Control (ASC) which holds engine RPM regardless of load, for example in a tight turn or when a skier applies pressure to a tow line, so that the captain does not have to adjust the throttle.
The 4.5L V6 and 6.2L V8 give the MerCruiser line a range from 200 to 350 horsepower in neat 50-horsepower increments, which Mercury says represent recognizable value for the consumer. In other words, you can feel the performance difference from engine to engine. The two power ratings of the 6.2L V8 are achieved by changing the calibration of the engine. The 6.2L V8 will replace the 300-horsepower 5.7-liter 350 MAG and 320-horsepower 6.2-liter 377 MAG choices in the MerCruiser line.
At the introduction event, I had a chance to try the new 6.2L MPI in several sterndrive-powered boats. The same Bryant Calandra we’d recently tested was on hand, now fitted with the intake resonator that was not on that early test boat, and it was indeed very smooth and very quiet. Super-quiet, in fact. When I demoed a couple of other boats, however, it became clear that Bryant is responsible for some of that quiet, as there was more engine noise apparent in other boats. It’s tough to gauge performance without a point of comparison, but I can say the 6.2L never disappointed on acceleration, and if you’ve driven a lot of different sterndrive-powered boats, you’ll immediately notice the smooth and responsive operation of the 6.2L.
In a nutshell, Mercury has set out to give boaters the technology it thinks is valuable—DTS, joystick control, ASC, and all the SmartCraft capability—with none of the technology it thinks has little application on the water. And the best way to do that was to start from scratch.
For more information, visit Mercury.