The Outboard Expert: Mercury Unveils 350-hp Super Verado At Miami Show
Boats.com's outboard expert gives you the exclusive first look at new supercharged outboard engine.
February 14, 2008
Revised from top to bottom, inside and out, the new Mercury Verado 350 SCi was engineered by Mercury Racing for high-performance offshore fishing boats. The new top cowl and gearcase can be seen in this image.
I've always suspected that Mercury Racing must be tinkering with a Verado outboard, and today at the Miami International Boat Show Mercury debuted the result - a hot new 350-hp "tuner" edition of the 2.6-liter Verado designed specifically for high-performance offshore fishing boats.
Under the Verado 350SCi cowl lurks a 2.6-liter, inline-six-cylinder powerhead that has been massaged into fighting shape by Mercury Racing, with 30 percent more supercharger boost pressure and a host of upgraded components.
The Verado 350 SCi was engineered by Mercury Racing, but will be sold as a standard Mercury outboard, which means any Mercury dealer or boat-building partner can order the motor, which will cost about $29,000. With fast fishing boats and especially the SKA tournament angler in mind, Mercury Racing tore into the Verado seeking more power and enhanced durability. This is the first four-stroke outboard to emerge from the Merc high-performance shop, and the project took three years to complete.
"The Verado 350 SCi is probably the largest engineering project ever undertaken at Mercury Racing," said John Skoski, who led the effort. "We have never worked with a four-stroke engine with a vertical crankshaft, and that presented some oiling challenges. But we are very pleased with the final result. This supercharged engine delivers great hole-shot and top-end performance."
With this new Verado, Mercury matches the king-of-the-hill horsepower rating of the Yamaha F-350, but the two motors have totally different missions. The Yamaha is designed to push big, heavy, wide-beam boats. The Verado 350 SCi is a speed-merchant built for full-throttle wave-hopping.
More Pressure for More Power
These polished stainless steel guide plates combine with hard-rubber motor mounts to help keep the Verado 350 SCi tracking true at high speeds and in rough conditions.
To increase power, Mercury Racing made a number of significant changes to the powerhead, the induction system, and the cowl. The powerhead retains the standard Verado 2598cc, six-in-line block but features a more-rigid cylinder head, more durable exhaust valves, new intake and exhaust camshaft profiles, and more-durable pistons and piston rings. New cooling jets bathe the bottom of each piston in oil, again to enhance durability. The WOT rpm range slides up to 6200-6800 rpm from the 5800-6400 range of the Verado 300, one reason there was so much focus on making the engine stronger. The other is a 30 percent increase in supercharger boost pressure. The 350 SCi uses the same supercharger housing as the standard Verado, but the rotor is a more-expensive piece that has been machined to tighter tolerances to improve its efficiency. The electronic boost relief valve was adjusted to permit higher boost pressure, but the supercharger pulley is larger in diameter to maintain the same supercharger rpm as the standard Verado even as engine rpm is higher. This motor will require 91-octane fuel.
The new cowl features an air-intake port on the front that directly feeds the intake tract cooler, higher-density outside air, rather than air that has been warmed under the cowl. A new intake attenuator (or muffler) offers more efficient airflow to the supercharger. Like all six-cylinder Verado models, an intercooler helps lower the temperature of the air charge after it has been compressed by the supercharger. A second vent on the top of the cowl feeds a new flywheel fan that helps regulate the air temperature under the hood.
The powerhead is supported by the same halo-like Advanced MidSection used on other six-cylinder Verado models, but there are a number of changes in this area of the motor. A new sand-cast driveshaft housing is thicker and stronger than the standard part, and solid rubber motor mounts improve tracking at high speeds. New stainless steel guide plates further help brace and support the motor. The exhaust tube was modified to reduce back-pressure by cutting windows in the bottom of the tube that allow some exhaust to flow out of the midsection just above the waterline. Finally, for added durability, the trim pin and steering head are supported by new impact-resistance bushing material.
A Bigger Leg
A new air inlet port on the front of the cowl feeds cool outside air through a filter and water-separating labyrinth directly to the Verado 350 SCi supercharger.
Mercury Racing determined that an all-new gearcase would be required for the extreme duty the Verado 350 SCi was likely to encounter. It is reportedly more hydrodynamic, and its larger size is designed to handle bigger gears with as-forged, straight-cut teeth, supported by a new billet-aluminum bearing carrier. The propshaft diameter is increased 25 percent to 1.25 inches, so this motor will use the Mercury Racing prop hub insert, but can run most Mercury or Mercury Racing propellers. The 350 SCi will have the same 1.75:1 gar ratio that debuted last year on the Verado 300, while its silver finish matches that of the Torque Master and Fleet Master cases used on Merc Racing two-stroke outboards.
The Verado 350 SCi will retain the drive-by-wire SmartCraft DTS controls and electro-hydraulic power steering introduced on the standard Verado models, and will compatible with other SmartCraft features, including Shadow Technology that allows three outboards to be controlled with two binnacle levers. The 350 SCi will be offered with a 20-, 25- and 30-inch shaft to accommodate single to quad installations on deep-vee hulls. The 25-inch version has a specified dry weight of 681 pounds, or about 32 pounds more than a Verado 300 and 164 pounds more than a two-stroke Mercury Racing Optimax 300XS outboard.
I'll be driving a Fountain rigged with triple Verado 350 SCi motors later this week at the Miami show, and will file a report on that experience right after the show.
Editor's Note: Charles Plueddeman is the editor at large for Boating, the nation's largest recreational boating magazine.
