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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

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Related news

Thursday, May 8, 2025

Offshore Vessels Feature MAN L21/31 GenSets for Diesel-Electric Propulsion

Construction of C-CSOVs trending towards China

Wenchong shipyard in China, part of the CSSC Group, has ordered four shipsets of 3 × MAN 8L21/31 MK2 GenSets in connection with the construction of 4 × 96m C-CSOVs (Construction and Commissioning Service Operation Vessels) operated by DO (Deutsche Offshore Schifffahrt [German Offshore Shipping]).

A CSOV is a specialised vessel designed to provide support services during the commissioning and operation phases of offshore wind farms. DO has innovated this concept with increased flexibility, offering the market enhanced applicability in the construction phase, as well as in the cable-grid sector. The basic design was drafted by Naval Architects Salt Ship Design AS from Norway. MAN Energy Solutions licensee, CMP, will build the engines in China with delivery scheduled from Q1, 2027; the order includes an option for further vessels.

The engines will be delivered as part-load optimised for increased fuel efficiency. They will also form part of an innovative diesel-electric concept that complies with Dynamic Positioning stage 2 (DP2), as set out by the DNV classification society.

Johannes Wolters, Managing Director of Deutsche Offshore, summarised: “MAN Energy Solutions’ L21/31 is a cornerstone in our endeavour to develop a vessel with a minimal environmental footprint. The engines offer us benchmark performance in the here and now, while granting us seamless readiness for our decarbonisation strategy.”

Colin Peesel – Head of Sales & Promotion, MAN Energy Solutions, Germany – said: “These 12 engines represent a very significant contract, amounting to over 20MW of power. The L21/31’s many advantages include its class-high fuel efficiency, and low noise-and-vibration levels. Crucially, it is future-proofed regarding operating fuel. Besides MGO, it is capable of running on biofuels such as HVO and FAME, and it is additionally delivered methanol-ready.”

The vessel design that allows for the future retrofitting of the L21/31 GenSets to methanol operation caters for this to a much higher degree than class notation actually requires. Having introduced substantial methanol infrastructure into the vessel already today will make a future conversion to carbon-neutrality smooth and efficient.

MAN Energy Solutions reports a growing trend within the offshore-vessel segment for construction to take place in China. The company already has a sizable presence in China supporting a broad network of licensee engine builders and a growing portfolio of new engine models. Likewise, its after-sales division – MAN PrimeServ – has a strong, global presence, regardless of where the DO vessels eventually operate.

Hakon Juel Hansen –  Manager Engine Promotion & Business Development – MAN Energy Solutions, said: “We are experiencing increased demand for efficient, competitive engine designs for the Offshore Wind segment, which our portfolio of small-bore propulsion engines is fulfilling, backed up by our MAN PrimeServ after-sales network. With these technically sophisticated offshore vessels, DO is showcasing the adaptability of our engine portfolio.”

About DO

Launched in 2024, Deutsche Offshore Schifffahrt (DO) is positioning itself as an important player in the rapidly growing offshore energy market. DO acts as commercial manager for four ordered special-purpose vessels, which have been ordered by Schoeller Holdings. These Construction and Commissioning Service Operation Vessels (C-CSOVs) are expected to enter service in 2027. The core task of Hamburg-based DO lies in the development of special offshore ships and the commercial operation of these technically sophisticated vessels tailored to the energy market. Technical management will be contributed by Columbia Energy.

 

The MAN 21/31H engine

Documents

  • PR DO C-CSOV 21.31_EN
    PDF, 247 KB English

Images

  • Red_6L_21_31
    JPG, 839 KB English
  • red_040425_update Illustration
    JPG, 864 KB English

Contact

Nils Søholt

Trade Press Marine

Group Communications & MarktingMAN Energy SolutionsTeglholmsgade 412450 Copenhagen SVDenmark

t +45 33 85 26 69

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