Wärtsilä 31 - the world’s most efficient 4-stroke engine
Wärtsilä 31 - the world’s most efficient 4-stroke engine

Wärtsilä 31 is a medium-speed 4-stroke marine engine that provides the best fuel economy of any engine in its class. Available in dual fuel, diesel, and pure gas versions.

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Wärtsilä 31 - the world’s most efficient 4-stroke engine

The Wärtsilä 31 is an efficient medium-speed 4-stroke marine engine that provides the best fuel economy of any engine in its class. It is available in cylinder configurations from 8 to 16 and with a power output ranging from 4.6 to 10.4 MW at 720 and 750 rpm. What’s more, it maintains its outstanding performance across the complete operating range.

It saves space because of its high-power output per cylinder. You will save time and money on maintenance thanks to its extended service interval and its high up-time.

The Wärtsilä 31 engine is available in diesel, dual fuel and pure gas versions.

Key benefits of the Wärtsilä 31

The Wärtsilä 31 retains its high efficiency and environmental values throughout the entire lifecycle of the vessel.

  • Lowest fuel consumption over its wide operating range
  • Remarkably high cylinder power, 650 kW/cylinder (diesel engine)
  • Meets the IMO Tier 3 regulations when operating on gas, and with a SCR when using diesel fuel
  • Ultra low emissions option for dual fuel engines in gas mode - an additional reduction of up to 85% in methane slip
  • Further energy savings with optional Smart Heat Recovery
  • Proven and reliable – running since 2018
  • Industry-leading lifecycle support maximising predictability and minimising costs

Who is it for?

Wärtsilä 31 is a perfect solution for ferries where operational flexibility, high power density, long intervals between overhauls, and high levels of safety are of paramount importance. Also fishing vessel and luxury cruise ship owners appreciate the Wärtsilä 31’s low noise emissions. The Wärtsilä 31 is designed to be suitable for a broad range of ship types and applications, in diesel electric configurations or as an auxiliary engine. And as the engine is available in diesel, dual fuel and pure gas versions you can easily choose a configuration that matches your requirements. 

Cut methane emissions with the Wärtsilä 31DF 

The Wärtsilä 31DF presents a new era for dual fuel engines with its ultra-low emissions when operating in gas mode. Get the same high output power than before and further reduce methane slip by up to 85 %. Besides you can remove nearly all NOx emissions.
The ultra-low emissions version of the engine is available for constant speed applications. 


reduction in methane


reduction in nitrogen oxides


reduction in greenhouse gas

CO2-eq (GWP 100)

Further emission reductions achieved on 50% load with the Wärtsilä 31DF ultra low emission version in gas mode compared to the standard Wärtsilä 31DF

Wärtsilä 31 and Wärtsilä 31DF Product guide and 3D models and drawings

Get technical data and system proposals for designing W31 and W31DF marine engine installations.

Customer stories

Discover the benefits others have already gained from Wärtsilä 31 engine.

  • The Ritz-Carlton Yacht Collection superyacht Ilma
    Ritz-Carlton Yacht Collection

    Wärtsilä 31DF dual-fuel engines with custom flexible mounting guarantee comfortable cruising aboard The Ritz-Carlton Yacht Collection’s Ilma superyacht.

    Learn more about the silent Wärtsilä 31 engine
  • Le Commandant Charcot

    Le Commandant Charcot, the world’s only luxury icebreaker, uses the Wärtsilä 31DF engines for sustainable polar exploration

    Read more about Wärtsilä 31DF engine with hybrid operation
  • Aurora Botnia - Fuel optimization

    Hybrid propulsion and flexible dual-fuel technology are just two of the ways ferry operator Wasaline is improving fuel efficiency and reducing emissions.

    Read more about the fuel optimization
  • Hammershus slide banner

    The first Wärtsilä 31 engines now in daily commercial operation

    Read more
  • Fishing-vessel-for-Peter-Hepsø-Rederi-AS
    Peter Hepsø Rederi AS

    The Wärtsilä 31 engine, which has been recognised by Guinness World Records as being the world’s most efficient 4-stroke diesel engine, has been chosen as the main engine for a new purse seiner/trawler.

    Read more
  • Fishing-Trawler-for-Strand-Senior-AS
    Strand Senior AS

    The best-in-class fuel efficiency of the Wärtsilä 31 engine means also that the exhaust emissions are correspondingly minimised.

    Read more
  • FSUE Atomflot
    FSUE Atomflot

    The new generation icebreaker Aker ARC 124 will feature three 8-cylinder Wärtsilä 31 engines.

    Read more

Insights on Wärtsilä 31

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