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    Marine gensets and auxiliary engines

    Fuel-efficient, emissions-compliant generating sets for all marine applications. Find your genset that meets your vessel’s power and feature needs with the Engine configurator.

    Find your genset in configurator

    Marine gensets and auxiliary engines for reliable ship power

    Wärtsilä marine gensets and auxiliary engines provide efficient, emissions-compliant auxiliary and diesel-electric propulsion power for ships worldwide. Choose from a wide range of diesel gensets, dual-fuel LNG gensets, and sustainable fuel options, all optimised for reliability and lifecycle performance. Configure your ideal genset today.

    Marine gensets and auxiliary engines – Key facts

    Wärtsilä marine gensets and auxiliary engines deliver efficient, IMO Tier III-compliant auxiliary power and diesel-electric propulsion for ships. Configure your ideal generating set today.

    • Purpose: Reliable auxiliary power for ships across all marine applications, with each Wärtsilä marine auxiliary engine engineered for performance and flexibility.
    • Fuel options: Diesel, dual-fuel LNG, and sustainable fuel alternatives.
    • Compliance: IMO Tier III emissions standards for global regulations.
    • Power range: Flexible configurations for small to large vessels.
    • Benefits: High fuel efficiency, low lifecycle costs, proven reliability.
    • Selection: Use Wärtsilä’s Engine configurator to match exact power and fuel needs.
    • Applications: Merchant ships, cruise ships, offshore vessel, ferries, and more.
    Contact our experts

    Find the right genset for your power needs

    Wärtsilä gensets are engineered for maximum efficiency and reliability across all marine applications. Selecting the right generating set is critical to ensure optimal operation for your vessel. Our portfolio includes electric generating sets suitable for both auxiliary power and diesel-electric propulsion covering power ranges from 0,74 MW to 10,4 MW and delivering high fuel efficiency, emissions compliance, and compact designs for easier integration. Explore the options below to match your exact power requirement and space availability.

     

      W20DF

      Wärtsilä 20DF generating setIMO Tier III
      Cylinder bore200 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke280 mmGenerator efficiency0.95 - 0.96
      Cylinder output160, 195 kW/cylFuel specification:Fuel oil
      Speed1000, 1200 rpm700 cSt/50°C 
      Mean effective pressure22.0, 21.0 barISO 8217, category ISO-F-DMX, DMA  & DMB
      Piston speed9.3, 11.2 m/sBSEC 8390 kJ/kWh at ISO cond.
      BSGC 8220 kJ/kWh at ISO cond.
      20DF, Rated power
       60 Hz50 Hz
      Engine type195 kW/cyl, 1200 rpm160 kW/cyl, 1000 rpm
      Eng. kWGen. kWEng. kWGen. kW
      6L20DF11701123960920
      8L20DF1560149812801230
      9L20DF1755168514401380

      Genset-20DF
      Dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*KL*Weight*
      6L20DF532520708951800273116.7
      975
      1025
      8L20DF6030207010251800279120.8
      1075
      9L20DF6535230010751800283123.7
      1125
      * Dependent on generator type and size. 

      W25DF

       

      Wärtsilä 25DF generating set
      IMO Tier III 
      Cylinder bore250 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke340 mmGenerator efficiency0.95-0.96
      Cylinder output315 / 345 kW/cylFuel specificationFuel oil
      Speed900 / 1000 rpm 6 cSt/40˚C
      Mean effective pressure25 bar  ISO 8217, category ISO-F-DMX, DMA, DFA, DMZ, DFZ. Biodiesel (FAME, HVO)
      Piston speed10.2 / 11.3 m/s BSEC 7560 kj/kWh at ISO conditions

       

       

      Wärtsilä 25DF, rated power    

      		60Hz50Hz
       315 kW/cyl, 900 rpm345 kW/cyl, 1000 rpm
      Engine typeEng. kWGen. kW (0,96)Eng. kWGen. kW (0,96)
      6L25DF1890181420701987
      7L25DF2205211724152318
      8L25DF2520241927602650
      9L25DF2835272231052981

       

       

      Wärtsilä 25DF, dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*K*L*Weight
      6L25DF7960272013602750385040
      7L25DF8620272013602750385045
      8L25DF9130272013602750385049
      9L25DF9900272013602750396055

       

      Genset-20DF

      W31DF

      Wärtsilä 31DF generating set
      		IMO Tier III
      IMO Tier II in diesel w/o SCR
      Cylinder bore310 mmFuel specification: Natural gas
      Piston stroke430 mm700 cSt/50°C 
      Cylinder output580, 600 kW/cylISO 8217 category ISO-F-RMK 700
      ISO-FDMA, ISO-F-DMB, ISO-F-DMZ, ULSF 
      Speed720, 750 rpm
      Mean effective pressure
      		29.8, 29.6 bar
      		SFOC (g/kWh) at ISO conditions   176.5 (diesel mode)
      Piston speed10.3, 10.75 m/sBSEC (kJ/kWh) at ISO conditions   7350 (gas mode)
      Generator voltage0.4-13,8 kV 
       Generator efficiency 0.95-0.97 
       31DF, Rated power
      Engine type
      		60 Hz50 Hz
      580 kW/cyl, 720 rpm600 kW/cyl, 750 rpm
      Eng. kWGen. kWEng. kWGen. kW
      8V31DF4 6404 4504 8004 610
      10V31DF5 8005 5706 0005 760
      12V31DF6 9606 6807 2006 910
      14V31DF8 1207 7908 4008 060
      16V31DF9 2808 9109 6009 220
      Wärtsilä 31 Genset dimensions
      31 DF genset, dimensions (mm) and weights (tonnes)
      Engine typeA*E*I* K* L*Weight 
      8V31DF9 4993 5941 7502 4005 00197.7
      10V31DF10 1673 5941 7502 4005 001109.7
      12V31DF11 6803 5941 8002 4004 944125.3
      14V31DF12 2043 5941 9002 4005 044142.1
      16V31DF12 8763 594 1 9002 4005 044155.2

      W34DF

      Wärtsilä 34DF generating setIMO Tier III, EPA T3
      Cylinder bore340 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke400 mmGenerator efficiency0.95 - 0.97
      Cylinder output480, 500 kW/cylFuel specification:Fuel oil
      Speed720, 750 rpm700 cSt/50°C 
      Mean effective pressure22.0, barISO 8217, category ISO-F-DMX, DMA & DMB
      Piston speed9.6, 10.0 m/sBSEC 7590 kJ/kWh at ISO cond.
      BSGC 7490 kJ/kWh at ISO cond.
      34DF, Rated power
      60 Hz 50 Hz
      Engine type 480 kW/cyl, 720 rpm 500 kW/cyl, 750 rpm
      Eng. kW Gen. kW Eng. kW Gen. kW
      6L34DF 2880 2770 3000 2890
      8L34DF 3840 3490 4000 3840
      9L34DF 4320 4150 4500 4320
      12V34DF 5760 5530 6000 5770
      16V34DF 7680 7370 8000 7680

      34DF power-up version, Rated power
       Generating sets
      Cylinder configuration720 rpm (60Hz)
      Engine [kW]Generator [kW]
      6L34DF31202990
      7L34DF36403490
      8L34DF41603990
      9L34DF46804490

      Wärtsilä 34DF power-up version is available only for in-line auxiliary engines.
      34DF Genset Dimensions
      34DF, Dimensions (mm) and weights (tonnes)
      Engine type A* E* I* K L* Weight*
      6L34DF 8700 2290 1450 2345 4000 57
      8L34DF 10410 2690 1630 2345 4180 76
      9L34DF 10475 2890 1630 2345 4180 87
      12V34DF 10075 3060 1700 2120 4365 96
      16V34DF 11175 3060 1850 2120 4515 121
      * Dependent on generator type and size.
      Generator output based on a generator efficiency of 96%.

      W20

      Wärtsilä 20 generating set
      		IMO Tier II or III
      Cylinder bore200 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke280 mmGenerator efficiency0.95 - 0.96
      Cylinder output185, 200 kW/cylFuel specificationFuel oil
      Speed900, 1000rpm700 cSt/50°C
      Mean effective pressure27.3, 28.0barISO 8217, category ISO-F-RMK 700
      Piston speed8.4, 9.3m/sSFOC 190,3 g/kWh at ISO condition
      Genset 20, Rated power
      60 Hz 50 Hz
      Engine type 185 kW/cyl, 900 rpm 220 kW/cyl, 1200 rpm 200 kW/cyl, 1000 rpm
      Eng. kW Gen. kW  Eng. kW Gen. kW  Eng. kW Gen. kW
      4L20 740 700 -   - 800 760
      6L20 1110 1055 1320  1255  1200 1140
      8L20 1480 1405 1760 1670  1600 1520
      9L20 1665 1580 1980  1880 1800 1710
      20-genset-dimensions
      Genset 20, Dimensions (mm) and weights (tonnes)
      Engine type A* E* I* K L* Weight*
      4L20 4910 1770
      1920      		 990 1800 2338 14.0
      6L20 5325 1770
      1920
      2070      		 895
      975
      1025      		 1800 2243
      2323
      2373      		 16.8
      8L20 6030 1920
      2070      		 1025
      1075      		 1800 2474
      2524      		 20.7
      9L20 6535 2070
      2300      		 1075
      1125      		 1800 2524
      2574      		 23.8
      * Dependent on generator type and size.

      W25

      Wärtsilä 25 generating set
      IMO Tier III 
      Cylinder bore250 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke340 mmGenerator efficiency0.95-0.96
      Cylinder output345 / 375 kW/cylFuel specificationFuel oil
      Speed900 / 1000 rpm 6 cSt/40˚C
      Mean effective pressure28 / 27 bar  ISO 8217, category ISO-F-DMX, DMA, DFA, DMZ, DFZ. Biodiesel (FAME, HVO)
      Piston speed10.2 / 11.3 m/s SFOC 182,7 g/kWh at ISO conditions

       

       

      Wärtsilä 25, rated power    

      		60Hz50Hz
       345 kW/cyl, 900 rpm375 kW/cyl, 1000 rpm
      Engine typeEng. kWGen. kW (0,96)Eng. kWGen. kW (0,96)
      6L252070198722502160
      7L252415231826252520
      8L252760265030002880
      9L253105298133753240

       

      Wärtsilä 25, dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*K*L*Weight
      6L257960272013602750380038
      7L258730272013602750380044
      8L259390272013602750389049
      9L259820272013602750389052

       

      Genset-20DF

      W31

      Wärtsilä Genset 31IMO Tier III
      IMO Tier II w/o SCR
      Cylinder bore310 mmGenerator voltage0.4–13.8 kV
      Piston stroke430 mmGenerator efficiency0.95–0.97
      Cylinder output630/650 kW/cylFuel specification: Fuel oil
      Speed720, 750 rpm700 cSt/50⁰C 
      Mean effective pressure32.4 / 32.1 barISO 8217 category ISO-F-RMK 700 
      ISO-FDMA, ISO-F-DMB, ISO-F-DMZ, ULSF
      Piston speed10.3, 10.75 m/sSFOC 169.4 g/kWh at ISO conditions
      Genset 31, Rated power
      Engine type60 Hz50 Hz
      630 kW/cyl, 720 rpm650 kW/cyl, 750 rpm
      Eng. kWGen. kWEng. kWGen. kW
      8V315 0404 8405 2004 990
      10V316 3006 0506 5006 240
      12V317 5607 2607 8007 490
      14V318 8208 4659 1008 735
      16V3110 080  9 67510 400  9 985
      Wärtsilä 31 Genset dimensions
      Genset 31, Dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*KL*Weight*
      8V319 4993 5941 7502 4005 00197.3
      10V3110 1673 5941 7502 4005 001109.2
      12V3111 6803 5941 8002 4004 944124.7
      14V3112 2043 5941 9002 4005 044141.5
      16V3112 8763 5941 9002 4005 044154.5
      *Dependent on generator type and size.

      W32

      Wärtsilä 32 generating setIMO Tier II or III
      Cylinder bore320 mmGenerator voltage0.4 - 13.8 kV
      Piston stroke400 mmGenerator efficiency0.95 - 0.97
      Cylinder output560, 580 kW/cylFuel specification:Fuel oil
      Speed720, 750 rpm700 cSt/50°C 
      Mean effective pressure24.9, 25.9 barISO 8217, category ISO-F-RMK 700
      Piston speed9.6, 10.0 m/sSFOC 174 g/kWh at ISO condition
      Genset 32, Rated power
      Engine type60Hz/720rpm50 Hz/750 rpm
      560 kW/cyl580 kW/cyl
      Engine kWGen. kWEngine kWGen. kW
      6L323 3603 2303 4803 340
      7L323 9203 7604 0603 900
      8L324 4804 3004 6404 450
      9L325 0404 8405 2205 010
      12V326 7206 4506 9606 680
      16V328 9608 6009 2808 910
      Genset 20 dimensions
      Genset 32, Dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*KL*Weight*
      6L328 345 2 490 1 450 2 3453 74557
      7L32 9 927 3 120 1 780 2 4224 20265
      8L3210 410 2 690 1 630 2 3454 01076
      9L3210 505 2 890 1 630 2 3454 01086
      12V3210 700 3 060 1 700 2 1204 130100
      16V3211 465 3 360 1 850 2 1204 445127
      * Dependent on generator type and size.

      W25A

      Wärtsilä 25 Ammonia generating set
      IMO Tier III 
      Cylinder bore250 mmGenerator voltage0.4-13.8 kV
      Piston stroke340 mmGenerator efficiency0.95-0.96
      Cylinder output280 / 305 kW/cylFuel specificationFuel oil, Ammonia
      Speed900 / 1000 rpm 6 cSt/40˚C
      Mean effective pressure22 bar  ISO 8217, category ISO-F-DMX, DMA, DFA, DMZ, DFZ. Biodiesel (FAME, HVO)
      Piston speed10.2 / 11.3 m/s  

       

       

      Wärtsilä 25 Ammonia, rated power    

      		60Hz50Hz
       280 kW/cyl, 900 rpm305 kW/cyl, 1000 rpm
      Engine typeEng. kWGen. kW (0,96)Eng. kWGen. kW (0,96)
      6L25DF1680161318301757
      7L25DF1960188221352050
      8L25DF2240215024402342
      9L25DF2520241927452635

       

      Wärtsilä 25 Ammonia, dimensions (mm) and weights (tonnes)
      Engine typeA*E*I*K*L*Weight
      6L257960272013602750380039
      7L258620272013602750380044
      8L259180272013602750389048
      9L259600272013602750389051

       

      Genset-20DF

      Why choose a Wärtsilä genset?

      Wärtsilä gensets are designed to meet the most demanding requirements for marine auxiliary power and diesel-electric propulsion. They are adaptable and ensure optimal performance throughout your vessel’s lifecycle. Key benefits include:

      • Efficiency that reduces operating costs and supports flexible operations
      • Compact footprint for easier integration and more space savings on board
      • Fuel flexibility, including LNG and ammonia dual-fuel capability, and methanol and methanol-ready options
      • Proven reliability and lifecycle support backed by Wärtsilä’s global service network

      Wärtsilä is recognized as one of the leading marine generator brands, trusted by ship owners and designers worldwide. When you choose Wärtsilä gensets, you’re choosing a partner committed to powering your operations with innovation, global expertise, and long-term support.

      Proven in service: customer references

      See how Wärtsilä gensets perform in real-world applications across diverse vessel types.

      • RRS Discovery
        RRS Discovery

        The Royal Research Ship Discovery is designed to support the multidisciplinary research required for the 21st century. The ship is the fourth vessel to bear the name and continues the tradition of oceanographic research at sea.

        Read more
      • RRS James Cook
        RRS James Cook

        The RRS James Cook operates worldwide in all climates - from the tropics to the edge of the ice sheets, enabling leading-edge multidisciplinary research.

        Read more
      • Want to see more success stories?

        Open the full reference library

      Frequently asked questions

      What is a marine genset and why is it important?

      A marine genset, a generating set, or a generator engine is an auxiliary engine that provides electrical power for ship systems and diesel-electric propulsion. It ensures reliable onboard energy supply for essential operations.

      What power ranges do Wärtsilä gensets cover?

      Wärtsilä gensets are available in power ranges from approximately 0,74 MW to 10,4 MW, covering requirements for small ferries to large merchant vessels.

      Are Wärtsilä gensets suitable for diesel-electric propulsion?

      Yes. Wärtsilä gensets are designed for both auxiliary power and diesel-electric propulsion applications, providing flexibility for different vessel designs.

      How compact are Wärtsilä gensets compared to alternatives?

      Wärtsilä gensets feature a compact footprint for easier integration and space savings on board, without compromising power output or efficiency. Dimensions are listed on this page for each genset model. Detailed performance data is available through the Wärtsilä Engine Configurator.

      Can Wärtsilä gensets operate on alternative and future fuels?

      Yes. Wärtsilä gensets are designed for fuel flexibility, including LNG, ammonia and methanol. A modular engine design ensures that Wärtsilä gensets are easy to convert to future fuels for most efficient operations throughout a vessel’s lifetime. Please contact us if you don’t find a genset model for a specific fuel you are looking for.

      Plan your auxiliary power solution with these resources

      Make informed decisions and streamline your design process with Wärtsilä’s expert tools and guides:

      Ready to specify your genset?

      Choosing the right auxiliary engine is critical for efficiency, space optimization, and future-proof performance. Our experts can help you match your vessel’s power needs with the ideal Wärtsilä genset configuration.

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