The Mercury Racing 300X Pro Max is a high-performance 3.0-liter, two-stroke V6 outboard designed for competitive and high-speed applications. It features advanced fuel injection, a high RPM range, and a lightweight yet durable build optimized for power and efficiency.
Engine Specifications
Type: Two-cycle, 60° V6
Displacement: 185 cu. in. (3044 cc)
Stroke: 3.00 in. (76.2 mm)
Cylinder Bore: 3.625 in. (92.075 mm)
Compression Ratio: 6.2:1
Peak Power Output: 300 HP (224 kW)
Full Throttle RPM Range: 6200 - 6800 RPM
Idle RPM (In Gear): 800 - 850 RPM
RPM Limiter: 7100 RPM
Peak RPM During Break-in: 5800 RPM
Fuel & Injection System
Fuel Injection: ECM-controlled, crank-angle-driven
Injectors: 6 individual injectors
Fuel Line Pressure: 39 ± 2 psi (268.9 ± 13.8 kPa)
Fuel Type: Unleaded gasoline (minimum 92 octane)
Fuel/Oil Ratio (ECM Controlled):
Idle: 250:1
WOT: 40:1
Fuel Pressure:
Idle: 2 psi (13.8 kPa)
WOT: 8 psi (55.2 kPa)
Ignition & Electrical System
Ignition Type: Digital Inductive
Firing Order: 1-2-3-4-5-6
Spark Plug Type: Champion QL77PP
Spark Plug Gap: 0.025 in. (0.63 mm)
Alternator: Delco Remy, 12V, 50A
Battery Requirements:
Minimum Marine Cranking Amps: 1000
Minimum Cold Cranking Amps: 800
Amp Hours: 105 Ah
Lubrication & Cooling
Oil Injection Type: Electronic oil injection
Recommended Oil: Quicksilver/Mercury TC-W3 Premium Plus 2-Cycle
Engine Oil Tank Capacity: 1.5 US qt (1.42 L)
Boat Oil Tank Capacity: 3 US gal (11.4 L)
Cooling System: Thermostat controlled
Thermostat Opening Temperature: 120°F (49°C)
Gearcase & Propulsion
Available Gearcases:
Fleet Master (1.75:1 ratio)
Torque Master (1.75:1 or 1.62:1 ratio)
Sport Master (1.75:1 or 1.62:1 ratio)
Gearcase Capacity: 28.0 fl oz (828 ml)
Reverse Gear Backlash: 0.030 - 0.060 in. (0.76 - 1.52 mm)
Water Pressure @ RPM:
Idle: 1.5 - 4.5 psi
5000 RPM: 10 - 12 psi
Midsection & Mounting
Shaft Length:
Standard: 20” (508 mm)
Long Shaft: 25” (635 mm)
Full Trim/Tilt Range:
Standard: 71°
Offshore: 72°
Power Trim Tilt: 19°
Steering Pivot Range: 60°
Maximum Transom Thickness: 2-3/8 in. (6.03 cm)
Guardian Engine Protection System
The Guardian System limits power in critical conditions:
Break-in Period: Limits power to 75%
Low Oil in Engine Tank: Limits power to 95%
Critical Low Oil: Limits power to 10%
Loss of Oil Pump Pressure: Limits power to 10%
Overheating/Low Water Pressure: Limits power between 95% and 10%
Battery Voltage Issues:
<12V: Decreases power to 50% at 11V, 0% at 10V
>16V: Reduces power to 50% at 17V, 0% at 18V
The Mercury Racing 300X 3.0L V6 is a powerful, high-RPM, performance-focused outboard designed for racing and high-speed applications. It integrates advanced ECM-controlled fuel injection, a Guardian protection system, and multiple gearcase options for durability and efficiency. The lightweight construction and high RPM range make it an excellent choice for high performance use.
Download the 6-page Mercury Spec Sheet in PDF - Free Online
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