Technology group Wärtsilä will supply its Wärtsilä 25 Ammonia auxiliary engine, together with a NOx reducer (SCR) and gas valve unit (GVU), for two new midsize LPG/liquid ammonia carrier vessels, each with a capacity of 51,350 m3. The engine will support reduced emissions and improved operational efficiency while helping the vessels meet evolving sustainability requirements.

The ships are being built at the Nantong CIMC Sinopacific Offshore & Engineering (SOE) shipyard in Shanghai and will be owned by Navigator Amon Shipping AS, a joint venture between Navigator Gas and Norway-based Amon Maritime. Wärtsilä will also supply the propulsion system, including a Controllable Pitch Propulsion solution designed to optimize efficiency and reliability. The order for the engines, SCR and GVU was booked by Wärtsilä in Q2 2026, while the order for the Controllable Pitch Propeller system was booked in Q3 2026.

Wärtsilä’s 25 Ammonia engine will help two new midsize gas carriers – owned by joint venture, Navigator Amon Shipping AS – reduce emissions, improve operational efficiency, and stay ahead of evolving sustainability requirements. © Wärtsilä Corporation

As the shipping industry transitions to decarbonized operations, ammonia is emerging as a carbon-free marine fuel capable of supporting the IMO’s net-zero-emissions target for 2050. Wärtsilä has developed engine solutions able to operate with alternative fuels and, in 2023, introduced what it described as the marine sector’s first commercially available four-stroke, engine-based solution for ammonia fuel. The ammonia-fueled engine supports the industry’s transition toward lower-emission vessel operations.

“By selecting the Wärtsilä 25 Ammonia engine, we expect to dramatically reduce the ships’ environmental impact, while supporting compliance with evolving regulatory requirements,” said Mr. Kaj S. Pilemand, Director of Vessel Operations, Navigator Gas.

When running on sustainable ammonia, total greenhouse gas emissions can be reduced by at least 90 percent compared with equivalent diesel engines. In addition, the Wärtsilä propulsion system optimizes vessel operations by integrating the entire shaft-line arrangement. The Controllable Pitch Propeller system is designed to deliver high efficiency, operational reliability and reduced emissions.

“This project reflects the continued momentum behind carbon-neutral and zero-carbon fuels, with ammonia emerging as one key pathway. It also highlights the growing demand for flexible propulsion solutions that support new, more sustainable operating models. In short, these vessels have been designed for lower-emission operations, and Wärtsilä’s solutions will support those ambitions,” said Stefan Nysjö, Vice President of Power Supply, Wärtsilä Marine.

The Wärtsilä equipment is scheduled for delivery to the yard beginning in June 2027.