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The Mercury Racing 450R V8 Outboard Engine is a high-performance 450 horsepower four-stroke outboard built around a supercharged 4.6-liter V8 powerhead. Developed by Mercury Racing for high-performance marine applications, the 450R combines forced induction, charge-air cooling, digital throttle and shift, electro-hydraulic power steering and purpose-designed Mercury Racing hardware in a package intended for demanding high-speed boats.
The 450R produces 450 HP / 336 kW and uses a 4.6-liter 64-degree V8 with 32-valve DOHC architecture. Mercury Racing specifies a 5,800–6,400 RPM wide-open-throttle range and offers the engine with either a 5.44-inch HD gearcase or Sport Master gearcase, depending on the application.
At the heart of the 450R is a 4.6-liter V8 with a 64-degree cylinder-bank angle, 32 valves and dual overhead camshafts. Mercury Racing designed the powerhead specifically for high-output marine performance, using a high-performance intake camshaft and race-spec Inconel exhaust valves.
The 450R’s induction system is centered on a 2.4-liter belt-driven twin-screw supercharger. The supercharger is water-cooled, while twin charge-air coolers reduce the temperature of compressed intake air before it reaches the engine. An electronic boost-control system and boost-bypass valve help manage boost across changing operating conditions.
| Specification | 450R |
|---|---|
| Manufacturer | Mercury Racing / Mercury Marine |
| Rated horsepower | 450 HP |
| Rated power | 336 kW |
| Engine type | V8 FourStroke |
| Cylinder configuration | 64-degree V8 |
| Valve train | 32-valve DOHC |
| Displacement | 4.6 L / 279 CID |
| Bore × stroke | 92 × 86 mm / 3.6 × 3.4 in |
| Induction | Supercharged with charge-air cooling and electronic boost control |
| Fuel system | Computer-controlled electronic fuel injection |
| WOT operating range | 5,800–6,400 RPM |
| Fuel requirement | Minimum 89 octane (R+M)/2 or 95 RON; maximum 10% ethanol |
| Charging output | 115 A / 1,449 W |
| Throttle and shift | Digital Throttle & Shift |
| Midsection | Mercury Racing Advanced MidSection (AMS) |
| Gearcase options | 5.44-inch HD or Sport Master |
| Gear ratio | 1.60:1 on specified configurations |
| Starting | SmartStart electric |
| Steering | Electro-hydraulic power steering |
| Dry weight | From approximately 689 lb / 313 kg, configuration-dependent |
| Warranty | 3-year limited warranty in published Mercury Racing specification |
The Mercury Racing 450R can be configured with either the 5.44-inch HD gearcase or the Sport Master gearcase. The correct choice depends on the hull, expected speed, mounting arrangement and intended operating conditions.
The Sport Master is a surface-piercing performance gearcase designed for high-speed applications. Mercury Racing documentation identifies it for boats capable of speeds above approximately 85 mph. The 5.44-inch HD gearcase is intended for more conventional submerged-propeller applications.
Do not select a gearcase solely by horsepower. Propeller type, engine height, hull design, water conditions and target operating RPM all affect the correct configuration.
The Advanced MidSection (AMS) uses heavy-duty guide plates and reinforced engine mounts to stabilize the outboard while isolating the powerhead from the transom. The design is intended to improve handling and reduce transmitted vibration in high-performance applications.
An optional rear tie-bar bracket integrated into the AMS provides a mounting point for multi-engine and catamaran installations where a tie-bar system is required. Exact rigging requirements should be established from the engine and boat manufacturer’s installation specifications.
The 450R uses Digital Throttle & Shift (DTS) rather than conventional mechanical throttle and shift cables. Mercury Racing lists compatibility with Zero Effort Digital controls and other Mercury digital control systems.
Electro-hydraulic power steering with an integral steering cylinder provides steering assistance suited to high-performance operation. Multi-engine boats can also be configured with compatible Mercury digital control and joystick systems where supported by the complete vessel rigging package.
The 450R is equipped with a 115-amp charging system, giving high-performance boats substantial electrical capacity for marine electronics, navigation equipment, audio systems, lighting and other onboard loads.
Mercury Racing also incorporates idle-charge battery management that can increase engine idle speed when additional alternator output is needed. Battery selection and cable sizing should follow Mercury’s installation requirements rather than being based solely on alternator output.
Mercury Racing specifies a minimum of 89 octane (R+M)/2 or 95 RON pump gasoline, with a maximum ethanol content of 10 percent for the documented 450R specification.
Published service information specifies Mercury Racing 25W-50 NMMA-certified FC-W synthetic-blend marine engine oil. The documented oil capacity with filter replacement is approximately 6.6 liters. Always verify the correct fluid specification for the engine’s serial number and service documentation.
The 450R has a wide-open-throttle operating range of 5,800–6,400 RPM. This extended range provides additional propeller-selection flexibility for high-performance applications.
Propeller selection should be based on actual boat testing. The engine should reach the manufacturer’s specified operating range under normal load and with the intended gearcase and mounting height. Incorrect propeller pitch or engine height can adversely affect acceleration, top-end RPM, cooling-water supply and engine loading.
The 450R is intended for high-performance boats, performance center consoles, offshore performance hulls, catamarans and other vessels engineered for high-output outboard propulsion. Its available gearcases, digital controls, tie-bar options and power steering allow the engine to be configured for different high-performance rigging requirements.
Because the engine produces 450 horsepower and weighs from roughly 689 pounds in its lightest published configuration, boat compatibility must be established carefully. Confirm the hull’s maximum horsepower rating, transom capacity, centerline mounting requirements, engine spacing and steering arrangement before purchase.
Installing a Mercury Racing 450R is a complete rigging project rather than a simple engine swap. Confirm the correct shaft length, gearcase, engine height, steering system, digital controls, battery capacity, fuel system, propeller and mounting arrangement.
Mercury Racing documentation lists 20-, 25- and 30-inch shaft configurations depending on the model. Published specifications also identify minimum centerline mounting requirements for multi-engine installations. Exact dimensions and spacing should be checked against the engine’s serial-specific installation documentation.
For multi-engine boats, the transom and structural system must be capable of carrying the combined engine weight and loads generated during high-speed operation. Professional rigging is recommended for high-performance installations.
The 450R combines a high-output supercharged engine with specialized cooling, lubrication and electronic-management systems. Maintenance should follow Mercury Racing’s service schedule and include engine oil and filter service, gearcase lubricant inspection, spark-plug inspection, cooling-system checks, fuel-system inspection and propeller examination.
The engine uses a high-capacity oil cooler and additional cooling-water management in the midsection. Keeping cooling passages, water pickups, anodes and the gearcase in good condition is particularly important when the engine is operated at high load.
For a used 450R, inspect service records and verify the engine’s serial number, ECU/diagnostic history, gearcase condition, steering components, supercharger system, cooling system and electrical connections before purchase.
The Mercury Racing 450R is rated at 450 horsepower, equivalent to approximately 336 kW.
Yes. The 450R uses a 2.4-liter belt-driven twin-screw supercharger with water cooling, twin charge-air coolers and electronic boost control.
The Mercury Racing 450R has a 4.6-liter / 279 CID V8 powerhead with a 64-degree cylinder-bank angle.
The published specification calls for a minimum of 89 octane (R+M)/2 or 95 RON gasoline, with maximum 10% ethanol.
The published wide-open-throttle operating range is 5,800–6,400 RPM.
The 450R is available with a 5.44-inch HD gearcase or Sport Master gearcase, with the appropriate configuration depending on boat type, speed and propulsion requirements.
The lightest published 450R configuration weighs approximately 689 lb / 313 kg. Sport Master and longer-shaft configurations can weigh more.
Yes. The Mercury Racing 450R uses Digital Throttle & Shift (DTS) and supports compatible Mercury digital control systems.
The Mercury Racing 450R V8 Outboard Engine combines 450 horsepower, a supercharged 4.6-liter V8, charge-air cooling, digital controls, power steering and specialized Mercury Racing gearcase and midsection technology. It is designed for high-performance vessels where propulsion output, rigging flexibility and high-speed capability are central to the installation.
Before ordering, confirm the exact 450R configuration, shaft length, gearcase, mounting requirements, steering system, controls and boat compatibility. You can also browse our outboard engines category to compare other marine propulsion options.
