MERCURY VERADO's Second Generation
Second Generation Mercury Verado Outboards Offer Cleaner Exhaust Emissions, Stronger Acceleration and Dramatically Better Fuel Economy
When Mercury Verado began life, the main claim to fame was raw, bloody horsepower. The turbocharged kind, ranging from 150 to 300 horsepower. Back in 2008 the entire line of Verado four-strokes was been redesigned to drastically reduce fuel consumption without compromising performance. Want hard numbers? Both dynamometer and on-the-water testing of the new 150 horsepower Verado shows 22 percent less fuel burned at wide-open throttle and 18 percent less fuel burned at cruising rpm (compared to last year's model).
Quick math says that with a 100 gallon fuel tank that's like getting 18 to 22 gallons of gas for free. Spend the dividend on either increased range or lower operating costs. More good news, all of Mercury's In-line 4 and In-Line 6 Verado outboards boast comparable fuel efficiencies.
This newfound mileage boost gives rise to the salient question: How'd they do what on paper seems like an impossible task? The answer is as simple as the sea is salt. Mercury went after internal friction. Friction is energy wasted, heat discarded out the exhaust or cooling system. Heat is what makes a piston go up and down and the crankshaft spin around and around. So naturally it follows that reducing parasitic friction frees up many thousands of BTUs worth of heat to convert directly into horsepower.
To that end, conventional cast-aluminum pistons were replaced with slippery forged pistons. They require less lubrication and they're much tougher. Cooling jets in the piston skirt were outright eliminated. The theory was that without oil squirting through now non-existent jets, there's less oil available to drip down cylinder walls and on into the crankcase.
Conventional connecting rod bearing inserts are grooved, with the groove running a full 360-degree circle. At rpm, a copious volume of oil flows through the groove lubricating the crankshaft journal and spills out over the sides. But not so with the new Verado bearing shells. Their innovative eccentric groove does not run full circle. So instead of a copious flow of oil flooding the crankshaft journal there is instead only a big puddle, an oil barrier between the big end of the connecting rod and the crankshaft journal. So as a result, less rogue oil slops over into crankcase.
On a conventional engine a machined surface on the underside of the cylinder block scrapes oil off the counterweight and unceremoniously dumps it into the sump. Mercury engineers tightened that clearance in order to scrap off a significantly larger quantity of rogue oil.
By now you're beginning to see a pattern in the engineer's madness. All these things, pistons, bearings and scraper, combine synergistically to reduce the amount of oil mist floating around freely inside the crankcase. Oil in suspension poses a considerable resistance the reciprocating mass (pistons, connecting rods and crankshaft) must overcome. With less rogue oil for the crankshaft to flail its way through, there is less friction to overcome.
> You should also know that fiddling with oil flow is not new. Hot rodders pushing the limits of the Chevy V-8 stretched out the springs in oil pumps to get more pressure. At least until they noticed how the high pressure oil flow was eroding crankshaft bearings. In the 1970's Toyota Motors and others played with low oil pressure oil pumps to free-up horsepower for stronger acceleration and better mileage. Mercury carried the ball over the goal line.
There's more to the story. Besides extreme oil management the camshaft grind was modified with higher valve lift and duration. Overlap, the interval during which intake and exhaust valves are open, is 10 percent longer. The speed at which valves ramp open or closed was accelerated. These are old school hot rodder tricks, tried and true, for building horsepower.
With lower friction bolstered by the performance modifications, horsepower soared through the roof. Tears in their eyes, engineers in white lab coats dutifully adjusted black box calibration, dialing back horsepower to the proper rated levels. A 200 horse remains 200 horsepower. But giving up the free horsepower and reducing friction significantly lowered fuel consumption, which was the point of the exercise in the first place.
What's particularly tantalizing about the Verado makeover is the question it poses: What might it mean for future motors, not just from Mercury Marine but also from all the other players? It seems likely others will study the lessons learned and apply them to their own production. And perhaps Detroit and Tokyo will work smarter, not harder, to improve the mileage of our tow vehicles.
Copyright 2007 by Tim Banse