Mercury 450R Supercharged 2020-2024 Service Manual

Mercury Racing's own confirmed marketing doesn't undersell the ambition behind this engine: "handcrafted by Mercury Racing for the high-performance disciple craving unrelenting power, the Mercury Racing 450R makes the paramount performance statement." Boating Mag's own confirmed engineering interview quotes Mercury Racing's head engineer directly on the genuine origin story: "this entire platform has been in development since 2013, and the Mercury Racing version of the 4.6-liter V-8 was always part of the program. Mercury certainly knows how to supercharge an outboard, so that aspect of the project was not a significant challenge. The toughest task was fitting our supercharged powerhead under the same slim-line cowl used for the normally aspirated versions of the V-8."

Power comes from a proprietary 64-degree aluminum-block 4.6-litre V8, topped with aluminum cylinder heads running Mercury Racing's Quad Cam Four Valve (QC4) DOHC design, chain-driven camshafts running in an oil bath (genuinely no timing belt to maintain), forged pistons, a high-performance intake cam profile, and race-spec Inconel exhaust valves, delivering a claimed 450 prop-shaft hp and 439 lb-ft of torque on 89-octane pump fuel — a genuine 40% torque increase over the outgoing Mercury Racing 400R. Boating Mag's own confirmed account details the actual forced-induction hardware: "a 2.4-liter belt-driven twin-screw supercharger is water-cooled to reduce the temperature of the intake air. Twin charge-air coolers reduce the temperature of the compressed intake charge," with a boost bypass valve automatically adjusting maximum pressure for changing ambient conditions.

Preferred Marine's own confirmed spec sheet lists a wide-open-throttle range extended to 5,800-6,400 rpm to broaden propping options, backed by a high-capacity oil cooler and an exclusive poppet valve in the midsection delivering higher on-demand cooling-water flow to manage the extra heat this supercharged configuration generates. TNT Custom Marine's own confirmed feature list details the Verado-style Advanced MidSection (AMS) with stainless-steel guide plates and stiffened engine mounts for genuine high-speed stability, a 115-amp alternator for demanding audio and electronics loads, Idle Charge battery management, and preprogrammed Transient Spark Technology tuned specifically for stronger hole-shot acceleration.

MBY's own confirmed weight comparison puts this engine's genuine achievement in perspective: at 313kg (689 lbs), the 450R weighs just 42kg more than the naturally aspirated 300hp Verado V8 it's based on, yet remains 129kg lighter than Yamaha's rival 5.6-litre XTO — all while fitting under the identical slim cowl used on the standard 300R, keeping center-to-center mounting distance at just 26 inches for genuine multi-engine transom installations. Boating Mag's own confirmed launch pricing lists $54,000-$64,000 depending on gear case and options, with the engine available in 20-, 25-, or 30-inch shaft lengths and Cold Fusion White or Phantom Black finishes.

This factory service manual covers the procedures, torque specs, and diagrams needed to keep a 2020-2024 Mercury Racing 450R running the way it was built to.