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Reliable and efficient four-stroke small-bore engines

Regulatory and fuel-related uncertainty can make it difficult to plan investments in propulsion and GenSets. With our small-bore engines, you are prepared for whatever lies ahead.

MAN Energy Solutions has built its position as the leading designer and developer of small-bore engines for the world’s merchant marine fleet on the basis of high reliability and efficiency.

Thanks to the low maintenance requirements, our engines provides extended lifetime, and additionally offer long time between overhauls (TBO). When needed, our service experts are there for you – every day and everywhere around the world.

MAN small-bore engine portfolio for the world’s merchant fleet

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More than
20000
MAN Energy Solutions small-bore engines are in service today
MAN PrimeServ
24
/7
service with passion
across the globe

Key benefits

  • Proven reliabilty

    Our small-bore engines are designed for lifelong operational reliability, availability and minimal downtime – they are ready and up running when you need them. Sturdy engine blocks, stiff crankshafts and robust connecting rods are just some of the basic design characteristics which secure trouble-free operation and long overhaul intervals.

  • High efficiency

    Efficient performance has a measurable effect on both the environment and your bottom line. It also explains why more than 19,000 of our engines are in service worldwide. Our dual-fuel engines let you select the most economic fuel type for the operating conditions. The cost optimized fuel injection system is also designed for high reliability and cost-efficiency.

  • Future-proof solutions

    The main uncertainties affecting engine choice have to do with the environmental and cost factors of fuel. Our answer is flexibility. Our single-fuel engines can run on conventional fuel types and also bio-fuel oils. Dual-fuel engines let you use methane as additional fuel type. The MAN L21/31DF-M and MAN L27/38DF-M can use methanol as second fuel type.  Our retrofitting expertise offers flexibility, now and in the future.

Full range of MAN four-stroke small-bore engines

Explore the capabilities and range of our engines.

GenSets and Diesel-electric propulsion

MAN L28/32DF GenSet

Based on the ultra-reliable and robust MAN 28/32H, the dual-fuel version is available as newbuild or retrofit and adds the ability to run on methane, with its economic and environmental advantages. High efficiency in gas and diesel mode makes it a perfect GenSet as part of a complete power package with four-stroke or two-stroke propulsion engines. Easy operation, easy maintenance and proven reliability also make it a trusted propulsion engine with long times between overhauls and low life cycle costs.

  • 720 – 750 rpm
  • 1,050 – 1,890 kW
  • 1,000 – 1,800 kWe

MAN L23/30H Mk3 GenSet

By applying innovative technology to classic design principles, the MAN L23/30H Mk3 is engineered to meet the power needs of most commercial ship types. Straight forward integration requirements make it a perfect choice for low-cost installation, while well-known maintenance procedures and common spare parts reduce operating costs. The new model raises power output per cylinder by 15-20% and reduces fuel oil consumption.

  • 720 – 900 rpm
  • 500 – 1,800 kW
  • 475 – 1,710 kWe

MAN L23/30DF GenSet

The MAN L23/30DF dual-fuel GenSet lets you select the most economic fuel for the operating condition. The cost optimized fuel injection system is designed for high reliability and cost-efficiency. It uses the main injection valve to inject pilot oil. This way, separate injectors, piping and pumps for main oil and pilot oil or a common rail system are not needed, saving on installation costs and maintenance. The monocoque design also eases the installation of the engine series and reduces weight.

  • 720 – 900 rpm
  • 625 – 1,320 kW
  • 590 – 1,255 kWe

This methanol-fuelled engine is a compact and reliable power source designed to run on methanol, heavy fuel oil (HFO), and most bio-fuel oils. When powered by green methanol, it is carbon neutral. The new engine type maintains the reliability and low consumption of the proven MAN 21/31, ensuring security of power supply on large vessels and handling load steps with confidence.

  • 900 – 1,000 rpm
  • 1,000 – 1,980 kW
  • 950 – 1,880 kWe

This GenSet operates at the lowest possible accumulated costs during their complete life cycle thus providing a safe investment.

A methanol conversion will be available soon as a retrofit for existing MAN 21/31 GenSets.

  • 900 – 1,000 rpm
  • 1,000 – 1,980 kW
  • 950 - 1,880 kWe

Propulsion engines

The robust and reliable MAN L27/38 delivers good performance over the entire load range with quick acceleration and immediate load response. Its proven reliability ensures long time between overhauls (TBO) and no unscheduled maintenance or repair work.

This engine is available as methanol-ready version.

  • 750 – 900 rpm
  • 2,100 – 3,690 kW

MAN L21/31 propulsion

The MAN L21/31 engine combines intelligent use of fuel in marine applications with flexible propulsion systems. It is the ideal power source, for example, for small to medium-sized tankers, cargo ships and ferries.

The proven engine is characterized by its reliability and low consumption. 

This engine is available as methanol-ready version.

  • 1,000 rpm
  • 1,290 – 1,935 kW
36000
h
time between overhaul extensions possible

Plan your vessel with confidence

Get in touch with our four-stroke small-bore experts for in-depth advice on all your propulsion and GenSet questions. Start your change process now and reach out to us today.

Contact our experts

Continue reading

  • Four- stroke marine systems
    pdf, 10891 KB

Related content

Related news

Tuesday, February 18, 2025

Type Approval Test Marks Important Milestone for Methanol GenSet

Dual-Fuel methanol MAN L21/31DF-M engine passes milestone in China

MAN Energy Solutions reports that its MAN 7L21/31DF-M (Dual Fuel-Methanol) GenSet has successfully passed its Type Approval Test (TAT) in China. The TAT was carried out in close cooperation with CSSC Marine Power (CMP) – the MAN Energy Solutions licensee – at CMP’s production facility in Zhenjiang and received approval from all major classification societies present at the event.

The basis for the new methanol engine concept is the MAN 21/31 Mk II type that is part-load optimised with a world-best specific fuel-oil consumption in the 1–2 MW range. The L21/31 engine is well-established in the market, having accumulated close to 3,000 sales over its lifetime. It burns heavy fuel oil/distillate according to the ISO8217:2024 specification, as well as other biofuels.

Michael Køel Andersen, Head of Testing, MAN Energy Solutions, said: “Integrating a methanol system into our well proven L21/31 engine has taken around two years, including some 18 months of intense testing at MAN Energy Solutions facilities. Being able to stand here today with an approved engine and concept – despite the tight timeline and intense R&D development that was demanded – is an important milestone for our business. It also demonstrates that our GenSets are agile and ready for the future market.”

MAN Energy Solutions states that the cost-effective, port fuel injection methanol concept now prominently positions the 21/31DF-M as the preferred, medium-speed, small-bore engine for GenSet and diesel-electric propulsion. It further states that the GenSet is a perfect match for its methanol-fuelled, MAN B&W ME-LGIM two-stroke engine.

Hakon Juel Hansen, Manager Global Promotion and Business Development, MAN Energy Solutions, said: “We have seen significant growth within the dual-fuel sector and market demand for fuel-flexible engines is strong. Sales of the 21/31DF-M have already reached double digits since its official market launch in 2024, showing that we are capable of providing solutions to power the merchant fleet in what is a period of uncertainty in terms of customer fuel-strategy.”

Hansen added: “This new methanol concept will add to the volume of over 30,000 GenSet and propulsion engines already provided to industry by our small-bore, four-stroke business unit. MAN Energy Solutions has continuously brought innovative engine concepts to the market, supporting the merchant maritime industry on its path to net zero. With this successful TAT, our customers now have another means of supporting their fuel strategy.”

The MAN 21/31DF-M engine

Documents

  • PR TAT L21.31DF-M_EN
    PDF, 246 KB English

Images

  • 21_31DF_M_Promotional_LeftBack
    JPG, 2482 KB English

Contact

Nils Søholt

Trade Press Marine

Group Communications & MarktingEverllenceTeglholmsgade 412450 Copenhagen SVDenmark

t +45 33 85 26 69

Available languages

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