Wärtsilä boosts ammonia engine power

The enhanced four-stroke engine now delivers 315 kW per cylinder at 900 rpm and 345 kW per cylinder at 1000 rpm, bringing it in line with the output of the LNG-fuelled Wärtsilä 25DF engine.

The increased rating means fewer cylinders are needed to meet power requirements, reducing installation complexity and simplifying maintenance while enabling more flexible vessel designs.

“With decarbonisation front and centre of our strategy, we continue to enhance the capabilities of our ammonia engine solution,” said Stefan Nysjö, vice president of Power Supply, Wärtsilä Marine.

“This power increase builds on our extensive testing and development work and helps make ammonia fuelled ship operations more practical and affordable, while maintaining high standards of safety and reliability.”

The upgraded engine also supports easier conversion between LNG and ammonia fuel operation. With a power range of 1.9–3.1 MW, it is suited for a wide variety of applications, both as a main propulsion engine and as an auxiliary unit. Aligning performance with the LNG variant improves retrofit potential, giving shipowners greater flexibility in fuel choices as the industry transitions to cleaner alternatives.

The higher output was successfully demonstrated during type approval tests conducted in autumn 2025 under the supervision of classification society representatives. The upgraded version is now commercially available, with deliveries scheduled from 2028.