Wärtsilä has upgraded its 4-stroke ammonia-fueled engine, the Wärtsilä 25 Ammonia, enhancing its power output to 315 kW per cylinder at 900 rpm and 345 kW at 1000 rpm. This new rating aligns with that of the LNG-fueled Wärtsilä 25DF engine, allowing for fewer cylinders to meet power demands, thus simplifying installation and maintenance.
This power boost facilitates the engine’s operation with both LNG and ammonia, providing a versatile range of 1.9-3.1 MW. The Wärtsilä 25 Ammonia can serve as either a main or auxiliary engine, improving retrofit options and offering shipowners greater flexibility in fuel choices. The upgrade was validated during type approval tests in autumn 2025, overseen by classification society representatives.
As the marine industry strives to meet international emissions reduction targets set by the International Maritime Organization, ammonia is increasingly viewed as a viable alternative fuel. The shift away from traditional fossil fuels is anticipated to accelerate in the coming years.
The enhanced Wärtsilä 25 Ammonia engine is now available for commercial delivery starting in 2028.
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