Mercury Debuts 450R Outboard

The highest-horsepower outboard engine to date from the U.S. builder

July 17, 2019
four mercury racing mr 450r outboard motors
Whether in single or multi-engine applications, the new 450R from Mercury Racing is an excellent choice for offshore power. Courtesy Mercury Racing

The new 450R from Mercury Racing features a 4.6-liter V8 powerhead, which is boosted by an exclusive Mercury Racing supercharger to produce 450 peak propshaft horsepower and 40 percent higher torque than the powerful 400R.

Considerable lighter than the nearest competitor, the new 450R delivers industry leading power-to-weight in a compact, efficient package. Multiple gearcase, control system, tie bar, and styling options are available to create the ultimate customized outboard performance package. The Mercury Racing 450R delivers all of its performance on readily available 95 RON pump fuel.

Designed and developed in-house and manufactured in Wisconsin on a dedicated Mercury Racing production line, the 450R is based on the same 4.6-liter V8 powerhead used for the normally aspirated Mercury Racing 300R outboard models. The proprietary 64-degree aluminum block is topped with aluminum cylinder heads with a Mercury Racing Quad Cam Four Valve design and double overhead camshafts. The valve train features a high-performance intake cam profile and race-spec exhaust valves. The camshafts are chain driven and run in an oil bath so there is no timing belt to maintain. Mercury Racing applies its supercharging expertise to extract incredible power from the 4.6- liter V8. A 2.4-liter belt-driven twin-screw supercharger delivers pressure charging with zero lag for instant throttle response.

mercury racing mr 450 outboard motor
The 4.6-liter V8 aluminum block is topped with aluminum cylinder heads with a Mercury Racing four-valve quad cam design and double overhead camshafts. Courtesy Mercury Racing

The supercharger is water-cooled to reduce the temperature of the intake charge and increase power. Twin charge-air coolers reduce the temperature of the compressed intake charge to further increase air density and power output. To maintain peak performance, a boost bypass valve automatically adjusts maximum boost pressure in response to changing ambient conditions. To better manage engine heat, the Mercury Racing 450R is fitted with a special high-capacity oil cooler and an exclusive poppet valve in the midsection to provide a higher volume of cooling-water flow on-demand.

Electronics and other engine components are designed and positioned to create the tightest package possible while maintaining good service access. The carefully considered design and placement of the new supercharger and charge-air coolers allow the 450R to use the same slim-line cowl as the 300R model while incorporating higher flow intake vents. Like all Mercury Racing outboards, the 450R accommodates 26-inch center-to-center mounting on multi-engine transoms.

Mercury Racing engineers addressed every aspect of performance in designing the 450R outboard, and the weight and design of each component was scrutinized to achieve maximum power with minimal weight. The result is outstanding power density; the best power-to-weight ratio for outboards rated 400 horsepower and above. The wide-open throttle operating range extends from 5800 to 6400 rpm, allowing for a full complement of Mercury Racing propellers to optimize acceleration, efficiency, and top speed.


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