Wärtsilä 31

The Wärtsilä 31 is the first of a new generation of medium speed engines, designed to set a new benchmark in efficiency and overall emissions performance.

The Wärtsilä 31 is available in 8 to 16 cylinder configurations and has a power output ranging from 4.7 to 9.8 MW, at 720 and 750 rpm. The launch of the Wärtsilä 31 introduces a 4-stroke engine having the best fuel economy of any engine in its class. At the same time, it maintains outstanding performance across the complete operating range. Its modular design enables a significant reduction in maintenance time and costs, thereby improving power availability and reducing the need for spare parts.

Wärtsilä 31 is recognised by Guinness World Records as the world's most efficient 4-stroke diesel engine

    The Wärtsilä 31 retains its high efficiency and environmental values throughout the entire lifecycle of the vessel.
    • Lowest fuel consumption over a wide operating range.
    • Highest cylinder power in its segment, 610 kW/cylinder.
    • Available in Diesel, Dual Fuel (DF) and Pure Gas (SG) versions.
    • Meets the coming IMO Tier 3 regulations when operating on gas, and with an SCR when using diesel fuel. The SCR has a minimal effect on fuel consumption.
    • Reliability guaranteed through extensive validation and Wärtsilä’s vast manufacturing experience.
    • Supported by Wärtsilä’s extensive global service network.
    Technical data
    Wärtsilä 31 IMO Tier II or III
    Cylinder bore 310 mm Fuel specification: Fuel oil
    Piston stroke 430 mm 700 cSt/50°C 7200 sR1/100°F
    Cylinder output 610 kW/cyl ISO 8217, category ISO-F-RMK 700 ISO-F-DMA, ISO-F-DMB, ISO-F-DMZ ,ULSF
    Speed 750 rpm  
    Mean effective pressure 30.1 bar
    Piston speed 10.75 m/s SFOC 167.7 g/kWh at ISO conditions
    Engine platform A A* B C F Weight (tons)
    Wärtsilä 8V31 6080 6417 3251 3111 1496 57,1 t
    Wärtsilä 10V31 6720 7057 3251 3111 1496 64,7 t
    Wärtsilä 12V31 7682 7833 3144 3460 1546 76,0 t
    Wärtsilä 14V31 8321 8473 3144 3460 1646 84.9 t
    Wärtsilä 16V31 8962 9113 3144 3460 1646 92,5 t
    Rated power
    Engine type
    8V31 4880
    10V31 6100
    12V31 7320
    14V31 8540
    16V31 9760
    W31 technical data W
    Download brochure

    The Wärtsilä UNIC is an embedded engine control system for Wärtsilä 4-stroke engines incorporating decades of experience, knowledge and expertise. It makes engines safe, environmentally energy efficient, reliable and flexible. Read more in the brochure. 

    Wärtsilä UNIC

    Specific fuel energy consumption
    • At ISO standard reference conditions at 85% load
    • Lower calorific value of fuel 42 700 kJ/kg
    • Tolerance 5%
    • With engine driven pumps



    The Wärtsilä 31 is designed to be suitable for a broad range of ship types and applications, both as a main propulsion engine and in diesel electric configurations, or as an auxiliary engine. It can be optimised for running either at constant speed or along a propeller curve. In the Offshore sector, the Wärtsilä 31 is a perfect solution for OSV´s and drilling or semi-submersible vessels, where operational flexibility, high power density, long intervals between overhauls, and high levels of safety are of paramount importance.

    Business White Paper - Hybrid propulsion is part of the future for RoPax ferries

    Business White Paper: Hybrid propulsion is part of the future for RoPax ferries

    Green is undoubtedly the colour concept most dominating today’s shipping industry, and nowhere is this more true than in the ferry sector. Environmental considerations are, along with the need to optimize operational efficiency, high on the agenda of ferry operators around the world.

    Hybrid systems are being featured more and more on a variety of vessel types, but are particularly relevant to ferries since they are more likely to be operating within areas covered by strict environmental regulations.

    Download this white paper to get a better understanding of how to select the most appropriate power system configuration for your RoPax or RoRo ferry, not only for today, but for tomorrow as well.


    • Car and passenger ferry for Mols-Linien
      A new 158 metre long car and passenger ferry being built for Danish operator Mols-Linien, will be powered by two 8-cylinder Wärtsilä 31 main engines.“The selection of this particular engine was based on the unique efficiency for the required output, and also the favourable maintenance intervals it allows.” Mols-Linien A/S - Technical Director Flemming Kristensen

      Car and passenger ferry for Mols-Linien

    • Fishing vessel for Peter Hepsø Rederi AS
      The fishing vessel will be powered by the Wärtsilä 31 engine and a complete propulsion system from Wärtsilä. “... a new vessel that will represent the future of the fishing fleet. Wärtsilä’s propulsion solution provides the efficiency and environmental sustainability we needed for the ship,” Audhild Hepsø, General Manager, Peter Hepsø Rederi AS.

      Fishing vessel for Peter Hepsø Rederi AS

    • Fishing Trawler for Strand Senior AS
      The vessel will feature the Wärtsilä 31 engine and propulsion machinery. “We wanted to build a new vessel that represents the future. For this reason we have emphasised high efficiency and environmental sustainability, and Wärtsilä was the obvious choice to meet these aims.” Strand Havfiske AS – Managing Director Janne-Grethe Strand Aasnæs.

      Fishing Trawler for Strand Senior AS

    • Icebreaker for FSUE Atomflot
      “We are convinced that Wärtsilä, with its long and good reputation as an engine builder, is able to build a reliable and efficient engine. Another feature in favour of the Wärtsilä 31 was the connection to the CBM (Condition-Based Maintenance) system. It is an advantage to us that Wärtsilä can monitor the engine operation online and, if necessary, provide us with instant advice.” FSUE Atomflot, Head of diesel-electric icebreakers, Alexander Degterev

      Icebreaker for FSUE Atomflot

    Find out what makes the Wärtsilä 31 tick

    Find out what makes the Wärtsilä 31...

    Next generation automation system enables Wärtsilä 31 performance. Download the brochure.

    Orders stream in for Wärtsilä 31

    The demand for ‘the world’s most efficient 4-stroke engine’, the Wärtsilä 31, shows no signs of slowing...
    28 March 2018
    • Twentyfour7. article

    Modularisation hand in hand with manufacturability

    The development of the new Wärtsilä 31 engine provided the perfect opportunity to exploit the benefits...
    29 May 2018
    • In Detail article

    Common rail fuel injection rules the...

    Very few marine engines are awarded a Guinness World Record. Thanks to Wärtsilä’s common rail injection...
    28 July 2017
    • Twentyfour7. article

    Next generation UNIC automation system...

    With its long history of technology leadership in advanced controls for medium- and low-speed combustion...
    21 July 2017
    • Twentyfour7. article

    Press releases

    Product hologram


    Wärtsilä engine in Guinness World Records

    The recently launched Wärtsilä 31 engine has achieved a Guinness World Records title for the most efficient...
    2 June 2015
    • News

    Wärtsilä 31 - the most efficient engine in the world

    Welcome to a brand-new generation of engines. The Wärtsilä 31 is setting a new standard for energy efficiency, delivering the lowest level of fuel consumption of any four-stroke engine worldwide.
    20 October 2015
    • Twentyfour7. article

    Wärtsilä 31SG, the world's most efficient...

    Wärtsilä's newest engine marks a step change in both efficiency and flexibility, delivering an industry-leading...
    15 November 2017
    • In Detail article

    The engine breaker

    Fredrik Grönlund has every little boy’s dream job: he breaks engines – or tries to – for a living. His...
    22 February 2017
    • Twentyfour7. article

    From Guinness world record to arctic...

    The world’s most efficient engine, Wärtsilä 31, has passed yet another milestone – a successful factory...
    9 November 2016
    • Twentyfour7. article

    Orders stream in for Wärtsilä 31

    The demand for ‘the world’s most efficient 4-stroke engine’, the Wärtsilä 31, shows no signs of slowing...
    28 March 2018
    • Twentyfour7. article

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