Splash247: Wärtsilä boosts ammonia engine output to match LNG twin

Bringing it in line with its LNG-fuelled equivalent and giving shipowners more flexibility when weighing fuel options.

The upgraded 4-stroke unit now delivers up to 315 kW per cylinder at 900 rpm and 345 kW at 1000 rpm, matching the output of the Wärtsilä 25DF LNG engine. The move means fewer cylinders are needed to reach the same power level, cutting installation complexity and easing maintenance requirements.

For designers, that translates into more efficient layouts and greater freedom when planning ammonia-fuelled vessels.The increased output also improves the case for switching between fuels. By aligning performance with the LNG version, Wärtsilä is aiming to make conversions between LNG and ammonia more straightforward, a key consideration for owners looking to hedge against fuel uncertainty.

The engine now covers a power range of 1.9 MW to 3.1 MW, opening it up to a broader set of applications, from main propulsion to auxiliary roles.

The higher rating was validated during type approval testing last year under class supervision, and the engine is now being offered commercially with deliveries from 2028.

Ammonia is gaining ground as a potential zero-carbon fuel, particularly as the International Maritime Organization tightens emissions targets and pushes the sector toward lower-carbon solutions.

While challenges remain around safety, infrastructure and cost, engine makers have been stepping up development to make ammonia a more practical option for deepsea shipping.

Wärtsilä said the latest upgrade builds on its broader ammonia programme and is aimed at improving both operational performance and overall project economics.

The Wärtsilä 25 platform itself is designed as a modular, medium-speed engine, allowing for easier integration across different vessel types and propulsion setups.

With owners weighing long-term fuel strategies, the ability to combine higher output with fuel flexibility is likely to be a key selling point as alternative fuel projects move from concept to delivery.