Twin Mercury 300R

The 300R is a performance-tuned V8 four-stroke outboard motor from Mercury Racing designed for high-speed sport boats, offshore applications, and competition use. It blends race-derived technology with four-stroke reliability for powerful acceleration and top-end performance.

300R” indicates the 300 horsepower rating as part of Mercury Racing’s R-Series performance lineup — an engine meant for aggressive power and precision handling on demanding boats.

The 300R produces approximately 300 HP (224 kW), giving strong thrust for performance hulls and larger boats.

It uses a 4.6 L V8 naturally aspirated four-stroke engine with dual overhead cams (DOHC) and 32 valves for responsive power and high-rpm performance.

The wide-open throttle operating range is about 5,800 – 6,400 rpm, where the engine delivers its best power and efficiency.

It runs on unleaded gasoline with at least 87 octane (R+M/2), or 90 RON, with up to 10 % ethanol (E10) allowed — regular fuel availability helps reduce operating cost.

The 300R features computer-controlled Electronic Fuel Injection (EFI) with Advanced Range Optimization for precise fuel delivery and better throttle response.

Yes — the 300R supports Digital Throttle & Shift (DTS) for smooth, precise electronic control, or mechanical controls for traditional feedback.

The 300R is available in 20″, 25″, or 30″ shafts so it can be matched to different boats and transom heights.

Yes — many performance boats use twin 300R engines for more total power, balanced thrust, and redundancy, though installation, rigging, and controls should be professionally engineered for safety and performance.

Yes — it can be paired with hydraulic or power steering, and optional tie-bar or side-bracket mounts for tailored steering response.

There are multiple gearcases — Torque Master for torque-focused performance and Sport Master for balanced speed and efficiency — with different gear ratios.

The 300R uses a water-cooled system with thermostat control and an integrated wet sump lubrication system to handle performance demands.

Engine oil and filter changes Lower-unit (gearcase) oil changes Water pump/impeller check Fuel and air filter service Corrosion protection and flushing after saltwater use

Yes — with appropriate corrosion protection and post-use flushing, it can be used safely in saltwater environments. Modern finishes and alloys help resist corrosion.

When properly maintained and used within appropriate operating ranges, the 300R offers robust performance and durability, drawing on Mercury Racing’s proven four-stroke technology. Regular service and quality fuel/oil help maintain reliability.

Yes — configurations (midsection, gearcase, controls, steering) are customizable, and many owners use aftermarket props and performance rigs. Professional setup and expert rigging are recommended for safety and optimal results.