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Reduce your carbon footprint with the new MAN L21/31DF-M methanol GenSet

The maritime industry is decarbonizing and methanol is currently one of the leading fuels among the alternative fuel solutions. Following the market demand and rising interest, we hereby introduce the new MAN L21/31DF-M methanol GenSet - the first small-bore dual-fuel methanol GenSet in our portfolio.

MAN Energy Solutions in Frederikshavn, Denmark is home of the MAN L21/31DF-M, our first small-bore GenSet fueled by methanol.

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reduction of lifecycle greenhouse gas emissions possible with e-methanol
conventional L21/31 engines in service

Proven GenSet design

The foundation of this new engine is based on the current L21/31 GenSet and its well-proven technology, which has already accumulated more than 110 million operating hours, with thousands of engines in service.

Key benefits

  • Low-emission fuel

    This engine runs on methanol or conventional fuels. When powered by green methanol, it has the potential to reduce greenhouse gas emissions. The possibility to operate GenSets on green methanol as drop-in fuel further increases the fuel-flexibility.

  • Reliability and low fuel consumption

    The new engine type keeps up the reliability and low fuel consumption of the MAN L21/31, ensuring security of power supply and handling of load steps with confidence. The power range spans 1,000-1,980 kW which makes this auxiliary engine the ideal candidate for most merchant vessels.

  • Retrofit options

    A methanol conversion will be available as retrofit for existing MAN 21/31 GenSets with delivery from 2025 onwards.

Perfect design features for efficient and reliable operation

The L21/31DF-M comes with a cost-optimised, low-flashpoint fuel supply system which makes it a competitive solution. 

Furthermore, the port fuel injection (PFI) concept provides additional simplicity and an attractive capital outlay. And it is based on proven components. 

Long time between overhaul intervals will save you time and costs on engine maintenance and will give you additional flexibility for the planning of your maintenance slots.

MAN L21/31 engine rendering

Technical specifications

DescriptionMain data


210 mm
Stroke310 mm
Speed900 / 1,000 rpm (60 Hz / 50 Hz)
Output1,000 – 1,980 kW
Cylinder configurator5 – 6 – 7 – 8 – 9
Available fuelsHFO, MDO, MGO, LSFO, ULSFO, Biofuels, MeOH
Emission limitIMO Tier III with SCR after-treatment


Optimized port fuel injection

The port fuel injection (PFI) system uses a methanol injection nozzle installed outside the combustion chamber. This simplified design removes the risk of blocked nozzles in diesel mode and reduces investment costs thanks to its easy installation and integration with standardized components.

MAN SaCoS control system and cybersecurity


MAN SaCoS ensures fast and reliable data-transfer between the engine and the power management system in the control room by easy cable connection.

The engine control system is attached to the engine and features a user-friendly color display in multiple languages. The electric speed governor enables fast response.

Perfect match for MAN B&W ME-LGIM two-stroke methanol engine


The first MAN B&W ME-LGIM came into service in 2016. Since then, we have accumulated more than half a million running hours on methanol alone, which provides a solid base for new developments. The L21/31DF-M is a perfect match for this methanol-fueled propulsion engine.

What makes the new methanol-fueled MAN L21/31DF-M GenSet special? Watch our 3D engine animation to find out more about the working principles, and also the Port Fuel Injection system.

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Service solutions for your equipment

MAN PrimeServ offers a range of modernization solutions for optimizing the reliability, availability, and economic efficiency. MAN’s upgrade and retrofit solutions are tailor-made to customers’ specific applications and equipment.

Go to MAN PrimeServ


Are you ready for green methanol?

Newbuild or retrofit? What are the costs? What are the benefits? Take the lead in sustainable shipping by contacting us today!

Contact us

Continue reading

  • PrimeServ Assist Four-stroke Brochure
    pdf, 4140 KB

Inside the making of a methanol GenSet

With the first two-stroke dual-fuel MAN B&W ME-LGIM methanol engines propelling large container ships across oceans, MAN engineers from Holeby and Frederikshavn, Denmark, are now developing the ideal match for onboard power: a small-bore GenSet capable of running on conventional fuel, biofuels and green methanol
Read the full story

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Related News

Set course to net zero with methanol GenSets - MAN L21/31DF-M

Watch the recording of our MAN ExpertTalk, where we introduced our new engine type: the small-bore four-stroke MAN L21/31DF-M GenSet for methanol operation.

You can look forward to hearing about this new GenSet type, the Port Fuel Injection (PFI) concept, the fuel gas supply system and the possibility to operate these GenSets on green methanol and biofuel oils.

    Register now