The MAN 32/40 is a medium-speed, four-stroke trunk-piston marine and stationary diesel engine produced by MAN Energy Solutions, with a 320 millimetre cylinder bore and a 400 millimetre piston stroke. The engine has been in continuous production since 1992 and is one of the most widely deployed medium-speed engines in the world, with installations spanning cargo vessels, ferries, cruise ships, naval auxiliaries, offshore support craft, dredgers, and stationary power plants. Cylinder configurations range from six in-line to eighteen in V configuration, with rated outputs from approximately 3,000 kilowatts to over 10,000 kilowatts.
Cylinder data and outputs
The 32/40 has a swept volume per cylinder of 32.2 litres and produces 500 kilowatts per cylinder at 720 revolutions per minute (60 hertz markets) or 480 kilowatts per cylinder at 750 revolutions per minute (50 hertz markets), with a brake mean effective pressure of approximately 23 to 25 bar in the most recent generation. Available configurations are L6, L7, L8, L9 in-line and V12, V14, V16, V18, giving a complete output range of approximately 3,000 to 10,800 kilowatts. The engine is supplied in the marine main propulsion variant (typically L configurations driving a reduction gearbox), the marine genset variant (typically L or V configurations driving an alternator at 720 or 750 revolutions per minute), and the stationary power-plant variant for diesel and heavy-fuel-oil baseload and peaking applications.
Fuel and emissions
The 32/40 is qualified for marine gas oil, marine diesel oil, heavy fuel oil, low-sulphur fuel oil, and (with the 32/40DF dual-fuel variant) liquefied natural gas with a small pilot diesel injection. The dual-fuel version operates on the Otto cycle in gas mode with lean-burn combustion and switches seamlessly to diesel mode on liquid fuel without interruption of power. IMO Tier II compliance is standard; IMO Tier III emission control area compliance requires either selective catalytic reduction (SCR) or operation in gas mode for the dual-fuel variant. The engine has been the basis for several MAN methanol and ammonia-ready conversion concepts announced in 2024 and 2025 as the company prepares for the energy transition fleet.
Applications
The 32/40 is among the most versatile platforms in the medium-speed segment. Notable application categories include:
- Container ship auxiliary gensets, where four to five 32/40 units typically share the auxiliary load on large container vessels.
- Ro-pax and ferry main propulsion, where two to four 32/40 units in mechanical or diesel-electric configurations supply ship-service and propulsion power.
- Cruise ship gensets, where six to nine units in V configuration feed integrated diesel-electric power plants.
- Offshore platform power generation, including FPSOs, drillships, and accommodation vessels, where reliability and heavy-fuel capability are decisive.
- Naval auxiliaries and large patrol craft, where the engine is selected for service-life and fuel-flexibility requirements.
The 32/40 has been licence-built or assembled by several MAN partners including Hyundai Heavy Industries Engine Machinery in South Korea and STX Heavy Industries in earlier years.
Comparable engines
In the same output bracket and bore class the 32/40 competes with the Wärtsilä 32, the Wärtsilä 31, the Caterpillar M32 series, the Bergen B32:40 (now B33:45 in revised form), the HiMSEN H32/40, and the Niigata 32FX. Each has distinguishing strengths: Wärtsilä 31 leads on thermal efficiency, the Bergen B33:45 leads on torque density, and the 32/40 leads on installed-base familiarity and global service network.
Service network
MAN Energy Solutions PrimeServ supports the 32/40 globally with approximately 100 service stations, original-equipment-manufacturer parts supply chains, and digital monitoring services including PrimeServ Assist. Engine bench tests at delivery and at major maintenance intervals are routinely performed at MAN’s Augsburg test bed for new build and at customer sites or HHI-EMD’s Ulsan test bed for licence-built engines.