Mercury 300 Engine

Mercury 300 Engine

The World’s Most Powerful Low Emissions Outboard

Suitable for

  • Bass Boats
  • Bay Boats
  • Catamaran Sport Boats
  • Flats Boats
  • Offshore Center Consoles
  • River Racers
  • Vee Bottom Sport Boats
  • Walleye Boats

In the News

Mercury Racing is all about passion for perfection and the pursuit of peak performance. We have a reputation of exceeding consumer expectations in product quality and performance – something we’ve carried forward from the late Carl Kiekhaefer, Mercury Racing president Fred Kiekhaefer’s father and founder of Mercury Marine. The all-new OptiMax 300XS outboard continues our heritage of delivering more power and performance than competitors with the same horsepower rating.

The heart of the new 300XS “Stroker” is a 3.2 Liter V-6 powerhead featuring a stroked and precision-balanced crankshaft for maximum power and performance. A dampener ensures smooth running throughout the engine operating range. New pistons feature an updated profile and a composite coating for improved wear life. Piston ring life is doubled thanks to a composite chrome coating.

The exhaust port, combustion chamber and fuel induction designs are direct descendants from our Formula 1 tunnel boat race engine. Airflow through the reed block fuel induction system is enhanced due an enhanced air box design along with thinner reed material and the unique reed shape developed for Formula 1 racing.

As with the complete line of Mercury Racing OptiMax XS outboards, the 300XS comes with a heavy-duty direct fuel injection air compressor featuring robust maxi-coated mounting brackets and hardware for enhanced compressor durability and reliability.

OptiMax 300XS Key Features

  • 3.2 Liter V-6 Powerhead features stroked and balanced crankshaft for maximum displacement and performance
  • Extensive R & D result in Formula 1 race based exhaust porting and reed block fuel induction design for top power
  • New combustion chamber design results in engine producing peak power longer at upper end of operating RPM range
  • A unique two-stage direct-injection system atomizes fuel into small, uniform particles, resulting with a complete and instantaneous combustion.
  • Fuel/air mixture is injected into the combustion chamber at 95 psi (15 psi higher fuel/air differential than standard DFI or OptiMax product) for enhanced high rpm running quality.
  • New PCM 07 microprocessor features a 14-pin Deutsch connector harness which incorporates engine ignition and SmartCraft CAN (controller area network) wiring in one connector
  • The SmartCraft Engine Guardian system monitors engine functions for early indications of problems that could lead to engine damage.
  • The 60-amp, belt-driven alternator is the most powerful in its class.
  • Electronic multipoint lubrication system delivers precise amounts of oil where and when it’s needed.
  • Acoustically tuned foam cowling wrap and new exhaust bucket design results with quieter engine sound throughout the operating range.
  • Through hull Noise Vibration Harshness (NVH) is further reduced on 25″ and 30″ models thanks to the used of softer upper and lower engine mounts.
  • A new exhaust system, along with a foam lined cowl and attenuator for the compressor greatly reduces the operating Dba.
  • Torque Master, Sport Master and new Heavy-Duty Fleet Master gearcases are enhance the versatility of the worlds most powerful available for virtually any application.
Engine Specs
Propshaft Rated Horsepower (HP / kW) 300 (224kW)
Full Throttle RPM Range: 5400-5800 (20″ models 5400-6100)*
Cylinders V-6 (60 degree vee)
Displacement 193 cu. in. (3160cc)
Bore & Stroke (in) 3.63 (92 mm) x 3.11 (79 mm)
Fuel Induction System 2-Stage Direct Fuel Injection
Ignition System PCM 07 Digital Inductive
Charging System 60-amp (756 watt) w/Voltage Regulator
Gear Ratio 1.62:1, 1.75:1 (SM), (TM) or 1.75:1 (FM)
Recommended Oil Mercury Premium Plus (TC-W3)
Fuel Requirements 91 Octane Minimum (R+M)/2 (96 RON)
Rotation Right or Left-Hand (FM), (SM) Right-hand (TM)
Shaft Length (inches) 20/25/30
Shaft Length (mm) 508/635/762
Weight (lbs / kg) (L) 505 lbs. (229 kg) (XL) 517 lbs. (235 kg) (XXL) 534 lbs. (242 kg)
Warranty Two-year limited warranty for recreational boating and three-year limited corrosion warranty. One-year limited Mercury Product Protection Plan available.