Japanese hydrogen 4-stroke high-speed engine receives double ClassNK approval

February 2, 2026, by Nadja Skopljak

Yanmar Power Solutions, a subsidiary of Japan’s industrial diesel engine and machinery manufacturer Yanmar Holdings, has obtained ship classification certification for its hydrogen-fueled four-stroke high-speed engine.

Demonstration model of a pilot-ignition hydrogen 4-stroke high-speed engine. Source: Yanmar

Yanmar Power Solutions reported on January 27 that it had become the first engine manufacturer in Japan to obtain both the type approval certificate and NOx certificate from Nippon Kaiji Kyokai (ClassNK) for its pilot-ignition hydrogen-fueled four-stroke high-speed engine for power generation for domestic coastal vessels.

The company used a small amount of hydrotreated vegetable oil (HVO) as a pilot fuel during its land-based demonstration tests, while preparing for planned demonstration operations.

As a result of ClassNK’s inspection, the company obtained the type approval certificate in October 2025 and the NOx certificate in December 2025, both required for demonstration operations.

The engine specifications covered by these certifications are designated as “Electronically Controlled Gas Only Engine (Hydrogen).”

Moving forward, Yanmar Power Solutions will install the necessary equipment, including two hydrogen engines, onto domestic coastal vessels, prior to demonstration operation trials scheduled for this fall.

The development is part of the Nippon Foundation’s Zero Emission Ships Project which focuses on the development of hydrogen-powered zero-emission vessels and supports related technology development.

Within this framework, the consortium involving Yanmar Power Solutions has been advancing hydrogen engine development, while also developing a hydrogen-compatible hybrid electric propulsion vessel that combines a hydrogen engine generator with batteries.

The vessel design incorporates a container unit-type hydrogen power generation system on its upper deck. Uyeno Transtech, a shipping company under the Uyeno Group, is responsible for the vessel’s development and construction.