Boat Motors

Mercury’s Introduces OptiMax Diesel Outboard

The Mercury Racing division has just introduced the second model in the cutting edge “Stealth” outboard engines. These new motors were developed for the U.S. Department of Defense who needed a low explosive and common-fuel run engine option for their use around the world.

The OptiMax Diesel Outboard is the first of its kind in the marine industry as the atomized diesel is then ignited by a spark instead of compression. A Propulsion Control Module microprocessor makes adjustments to the fuel and spark timing to optimize performance across the operating range of the engine.

Theses 3.0 Liter V-6 Diesel can produce 175 propshaft horsepower and is very similar to the gas burning versions. Only 5% of the parts are different which keeps training requirements to the minimum.

OptiMax Diesel is an industry exclusive spark ignited diesel engine. Glow plugs ensure consistent, reliable cold starting.


  • Mercury Racing cylinder heads designed specifically for combusting diesel fuel.
  • High performance cylinder liners for maximum horsepower and optimal engine running quality.
  • Fuel/air mixture is injected into the combustion chamber at 95 psi (15 psi higher fuel/air differential than standard OptiMax product) for enhanced high rpm running quality.
  • Custom calibrated Propulsion Control Module (PCM) microprocessor optimizes fuel and spark timing for enhanced running quality and performance.
  • SmartCraft Engine Guardian provides real-time, selfprotection engine fault diagnostics and messaging.
  • Electronic multipoint lubrication system delivers precise amounts of oil where and when it’s needed.
  • Multi-strike ignition coils fire spark plugs up to seven times per revolution for a complete fuel burn, eliminating any chance of misfire.
  • The 60-amp, belt-driven alternator is the most powerful in its class.
  • Acoustically tuned foam cowling wrap and new exhaust bucket design results in quieter engine sound throughout the operating range.
  • Stealthy tone-on-tone graphics featuring the new Mercury Racing word mark.

Built as military engines now, but I’m sure the technology will cross over to other products in the future.

You can check it out on Mercury’s site.