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Overview of the Supercharged Mercury Racing 450R

Outboard motor horsepower is climbing furiously like the red needle on a tachometer. Awhile back Yamaha Marine unveiled its 425-hp V8 outboard. Mercury Racing responded with its 450R. Here is that engine's story, that of a supercharged 450-horsepower version of a 4.6-litre V8 engine.

Learn About Mercury Racing's Supercharged 450-horsepower 4.6-Liter V8 outboard

Two Mercury Racing 450R GWWRS models

Mercury Racing's 450R is based on the same 4.6-liter V8 block used for the normally aspirated Mercury Racing 300R outboards. That means aluminum cylinder heads spinning Mercury Racing's Quad design valve train. More specifically, 4-Valves per cylinder and double, overhead camshafts (DOHC). The benefit of having four valves per cylinder is the way they maintain port velocity at low rpm and yete still flow huge volumes of air at high rpm. This pays dual dividends in razor-sharp acceleration all the way up and down the rpm band. No big surprise, being incarnated as a race motor, the camshaft lobes are ground to a high-performance profile (intake side). Cams are chain-driven and rotate in an oil bath.

450R is based on the all-aluminium, 300 horsepower Verado V8 with an unusually narrow, 64-degree block

Mercury Racing's 450R Valvetrain

Mercury Racing's 450R replete with DOHC and 24-Valves

The cylinder head has been lovingly populated with a set of 16 Inconel (751 Nickel Base Alloy) exhaust valves. Savvy builders believe Inconel exhaust valves are an absolutely necessary component in turbo'ed and supercharged marine engines for the way they stand up to very high temperatures, and actually run cooler with lessened risk of warping/failure. Mercury Racing bills the 450R as a: "go-full-bore-all-day-long," engine. Inconel valves are one of the reasons they can make that claim.

50R draws its breath from a sizezable, 2.4-liter belt-driven twin-screw supercharger. Compared to a turbocharger there is no throttle lag when you punch the throttle, because there is no wait for the turbo to spool up and begin pushing air. The supercharger is water-cooled which reduces the ambient temperature of the intake charge. This is simple physics. A cooler air-charge is denser so it packs more horspower potential into the combustion chambeer. Moreover, twin intercoolers further reduce the temperature of the compressed intake charge, once again, increasing air density and horsepower.

Mercury Racing's 450R Valvetrain

A twin scroll supercharger neatly tucked between the V8's cylinder banks

Superchargers are also notorious for their high-pitched whine. But that's not a problem with this beast because the otherwise annoying noise is suppressed by a special intake attenuator that neutralizes whine while at the same time retaining the deep, soul-stirring, exhaust notes that cause our pulses to quicken. The benefit of a belt-driven supercharger over a naturally-aspirated engine, especially in a performance engine, is the way that it boosts low rpm torque and peak power without massive cubic inches that would otherwise increase unit cost and take up more room on the transom. 450Rs supercharger sits daintily in the valley of an all-aluminium, cylinder block. The twin brother to the 300-horsepower Verado, it boasts an unusually narrow, 64-degree, V8. Its narrow profile pays big dividends. Centre-to-centre measurement is a mere 26-inches which in turn means twin, triple or even quad installations on transoms.

For comparison, with its supercharger, 450R makes 40% more torque than the already potent Mercury 400R. The real eyebrow raiser is the way high-performance 450R burns common, fuel dock, 89 octane (95 RON) unleaded gasoline. Unlike some monster motors hungrily lurking on the waters, 450R does not require the more expensive and sometimes hard to find, super unleaded fuel.

cutaway illustration of a 450R SportMaster Gearcase a CNC'd racing propeller

the new 450R models, the popular MAX5 and Outboard CNC Cleaver props are required for use with the surface piercing Sport Master gearcase. The standard 450R has a 5.44HD submerged gear case for boats up to 74 knots

From single-engine performance runabouts ranging to multi-engine catamaran sport boats Sport Master gearcase, given the correct application, enhances boat handling, speed and efficiency. More particuarly, the Sport Master is designed for boats capable of speeds in excess of 85 mph. It features low water pick-ups and a crescent leading-edge. 450R engines feature a robust, one-piece, 3.2 cm/1.25-inch in diameter, stainless steel propshaft. Think tough as nails. For single-engine boats, an optional, cambered skeg counteracts prop torque lending improved handling. 450R is also available with the 5.44 HD gearcase for lower-speed and traditional submerged applications. All 450R gearcases feature a 1.60:1 gear ratio for stronger acceleration.

On Mercury Racing 450R either MAX5 or Outboard CNC Cleaver props are required for use with the surface piercing Sport Master gearcase. For 5.44 HP gearcase applications, Mercury Racing’s Bravo I FS, Bravo I LT, Enertia ECO XP and Rev 4 XP are worthy options.

The 450R is compatible with Mercury Racing Zero Effort Digital controls, or for that matter, any Mercury Marine digital control system capable of managing as many as six outboards with a single lever. Digital throttle and shift technology are standard, with Joystick Piloting for Outboards (JPO) available for boats rigged with two to six outboards.

With wide-open throttle ranging from 5,800- to 6,400-rpm, an extensive array of different propeller options are offered in order to to best suite the size and weight of the hull. Besides a plethora of different propeller options, the 450R outboard can be specified with either of two different gear cases. The first is the 5.44 HD gear case designed for traditional, submerged propeller applications on boats boasting a maximum speed of 74-knots (85-mph), while the optional Sport Master gear case is designed for surface-piercing applications on race boats and high performance leisure craft. Rear tie-bar brackets are available for multiple engine applications on high-speed craft.

Mercury Racing 450R rigged on a very fast catamaran

Rear tie bar brackets for both race boats and high-speed, leisure catamarans

Finally, Electro-hydraulic steering is standard, as are: Joystick control on multi-engine installations; A pop-up hatch in the cowling allows for spur of the moment oil checks and top ups. A robust, 115-amp alternator provides lots of juice for audio systems and electronics. should the Idle Charge battery-management system sense low battery voltage it automatically increases engine idle rpm boosting output until batteries are fully charged. The 450R outboard is backed by a three-year, limited factory warranty and a three-year limited corrosion warranty. For a little more money coverage can be extened for up to five additional years with Mercury's Product Protection, a factory-backed extended service plan.

portrait of Claus Bruestle

Mercury boasts significant experience with supercharging outboard motors by way of its first generation, 2.6-Liter I-6, Verados. Be it known Claus Bruestle was the chief architect of the Verado project during his tenure at Mercury (2002-2007 ). Previously he worked at Garret AiResearch, renowned for forced-air induction gas engines and pioneering some of auto racing's technology milestones, including the first turbocharged engines to win at Indy and the 24-Hours of Le Mans. Later Bruestle was an engineer at Porsche (15-years) where he developed its Formula One engine program and led the team that developed the Porsche Cayenne V8 engine.

Mercury Racing 450R Specifications
Configuration 64° V8
Displacement CID
4.6-Liters
Induction Supercharged
Bore x stroke 92mm x 86mm
Maximum rpm 5,800-6,400rpm
Maxmum power 450
Idle speed 600 rpm
Weight 313-324kg
Warranty Term 3-year limited

As for price point, depending on the model, MSRP ranges from $54,000 to $64,000. More particularly, standard shaft/transom height, HD gear case models are on the lower end of the scale with Sport Master with rear tie bar (catamarans) priced on the higher end.