Mercury Racing 450R Cranks Up the Volume

New Mercury Racing 450R Outboard Revealed

June 19, 2019
Mercury Racing 450R running at speed
Mercury Racing claims the 450R cranks out 450 propshaft horsepower and 439 ft. lb. of torque. Courtesy Mercury Racing

Mercury Racing is about to turn up the volume on outboard performance with the introduction of its all-new 450R model, a 4.6-liter V8 with an all-new supercharger system. This new high-performance outboard supersedes, but for now will not replace, the popular Mercury Racing 400R. Mercury Racing claims the 450R cranks out 450 propshaft horsepower and 439 ft. lb. of torque on 89-octane pump fuel – 40 percent more torque the Mercury Racing 400R, yet at 689 pounds the 450R weighs just 21 pounds more than the six-cylinder 400R.

According to Mercury Racing Director of Marketing Steve Miller, the new 450R models will have a price range of $54,000 to $64,000 depending on gearcase and other options – about 50 percent more at retail price than Mercury Racing 400R.

Mercury Racing 450R with Sport Master gearcase
The 450R is the first all-white outboard from Mercury Racing, shown here with the Sport Master gearcase option. Courtesy Mercury Racing

“We see a migration from the 400R to the 450R for the biggest performance boats,” said Miller, “center console boats over 50 feet, for example. There are customers who just want the most power they can have no matter the cost, but with this new platform you’ll also get a lot of technology and features that are just not available on the 400R. There are also going to be boats that just can’t handle the 450R, and those customers will still be able to run the 400R.”


Mercury Marine is already having trouble meeting the demand for the mainline versions of the 4.6-liter V8 like the Verado 350 and Pro XS 300, and Miller says that availability of the 450R will be limited for 2019, with production earmarked for performance boat builders and very few left for re-power installations through dealers.

The new Mercury Racing 450R is based on the naturally aspirated Mercury Racing 300R outboard, which in turn has as its foundation the 4.6-liter double overhead-cam, four-valve 64-degree V8 platform used across four Mercury outboard series: Verado, FourStroke, Pro XS and Ocean Pro.

“This entire platform has been in development since 2013, and the Mercury Racing version of the 4.6-liter V8 was always part of the program,” said Mercury Racing head engineer Jeff Broman. “Our team collaborated with the mainline engineering team to make sure that the basic engine design could handle the loads we anticipated would occur at the power level Racing had targeted.


“Mercury certainly knows how to supercharge an outboard, so that aspect of the project was not a significant challenge,” said Broman. “The toughest task was actually packaging our supercharged powerhead to fit under the same slim-line cowl used for the normally aspirated versions of the V8.”

Mercury Racing 450R supercharger
In this view of the Mercury Racing 450R the supercharger and the port-side charge-air cooler (copper coils visible) can be seen. Courtesy Mercury Racing

Designed and developed by Mercury Racing and manufactured in Wisconsin on a dedicated Mercury Racing production line, the 450R features a Mercury Racing Quad Cam Four Valve (QC4) cylinder head design. The valve train features a high-performance intake cam profile and race-spec Inconel exhaust valves. The camshafts are chain-driven and run in a oil bath so there is no timing belt to maintain. A 2.4-liter belt-driven twin-screw 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 with minimal airflow restriction. The supercharger and charge-air coolers occupy the space filled by the intake tract on the normally-aspirated V8 outboards.

“The normally aspirated V8 motors have a large intake plenum and long runners on both sides of the block to boost torque,” said Broman. “With the supercharger pumping air into the engine that intake tract is not required, so we had that space to work with.”


A boost bypass valve automatically adjusts maximum boost pressure in response to changing ambient conditions. A high-capacity oil cooler and an exclusive poppet valve in the midsection to provide on-demand higher volume of cooling-water flow help manage the increased engine heat produced by this high-performance engine.

Cutaway of the Mercury Racing 450R
The cutaway of the Mercury Racing 450R shows the twin-scroll supercharger placed on the front of the powerhead. Courtesy Mercury Racing

Gearcase options include the Mercury Racing Sport Master for boats capable of speeds in excess of 85 mph – now with a new one-piece 1.25-inch diameter stainless steel propshaft – and the 5.44 HD for lower-speed and traditional submerged applications. Both gearcases come with a 1.60:1 gear ratio. The wide-open throttle (WOT) operating range peaks at a generous 5800-6400 rpm, a broad window for propping options. The Mercury Racing MAX5 and Outboard CNC Cleaver props are required for use with the Sport Master gearcase. For 5.44 HD gearcase applications the Mercury Racing Bravo I FS, Bravo I LT, Enertia ECO XP, and Rev 4 XP are available. The 450R will be offered in 20-, 25- and 30-inch lengths.

The 450R has the Verado-style Advanced MidSection (AMS) with stainless steel guide plates and stiffened engine mounts for improved engine stability and high-speed handling. The AMS has an integral tie-bar mount, and enables optional Joystick Piloting for Outboards (JPO) for boats rigged with two to six outboards. Other features carried over from the base 4.6-liter platform include a 115-amp alternator to handle big audio systems and power-hungry angling accessories, the Idle Charge battery-management system that bumps up idle rpm when it senses low battery voltage, and pre-programmed Transient Spark Technology that adjusts timing advance for stronger hole-shot performance. Adaptive Speed Control with a Mercury Racing calibration automatically holds engine rpm regardless of load or condition changes. The nifty Top Cowl Service Door makes routine engine oil checks a breeze.

Tie-bar mount on the 450R
The AMS has an integral tie-bar mount. Courtesy Mercury Racing

It’s kind of amazing that this high-performance outboard is backed by a three-year limited factory warranty and a three-year limited corrosion warranty – just like the plain old black Mercs. Color options include Cold Fusion White with Devil Red Eye cowl accent panels and a white Advanced MidSection (AMS) and gearcase, and Mercury Phantom Black with Graphite Grey cowl accent panels and matching Graphite Grey AMS and gearcase. A Carbon fiber and paint-ready accessory accent panel kit will be are available to custom-match a 450R outboard to a boat color scheme.

For more information: Mercury Racing


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