Japan Engine Corporation completed land-based operation tests on what it calls the world's first hydrogen-fueled engine built for a large merchant ship, giving the marine industry a first hard number for how far hydrogen combustion has advanced. In factory testing, the engine, model 6UEC35LSGH, ran with a hydrogen co-firing ratio above 95%, meaning more than 95% of its fuel input by that measure was hydrogen rather than heavy fuel oil. Greenhouse gas emissions fell by more than 95% against a comparable conventional heavy-fuel-oil engine.
NEDO, Japan's public energy and industrial technology agency, announced the result on September 8, 2026, a day after Japan Engine unveiled the engine at its head-office plant. The company reached the co-firing rate using high-pressure direct injection, which feeds hydrogen straight into the cylinder under pressure rather than pre-mixing it with air, plus a leak-prevention structure and double-walled hydrogen supply piping for safety. ClassNK, the ship classification society, witnessed the approval tests, which the release says were completed without issue, and will keep assessing safety through the vessel's design, construction and operating stages.
The project runs under NEDO's Green Innovation Fund program for next-generation ships, with Japan Engine developing the engine alongside Kawasaki Heavy Industries and Yanmar Power Solutions. Kawasaki is separately building the Marine Hydrogen Fuel System, the tank and supply setup that will feed the engine hydrogen at sea, plus the liquefied-hydrogen bunkering equipment needed to load ships with the fuel. It is Japan Engine's second marine "world-first" fuel claim in just over a year: the company completed a commercial ammonia-fueled two-stroke engine in August 2025. The hydrogen engine's world-first claim is qualified in the release's own footnote as based on Japan Engine's review of the field as of September 2026.
| Event | Date |
|---|---|
| World-first ammonia-fueled two-stroke marine engine completed | August 2025 |
| Hydrogen-fueled engine 6UEC35LSGH completed; land-based test success | September 2026 |
| Engine installation on 17,500-DWT multipurpose vessel | January 2027 |
| Actual-vessel demonstration voyages begin, after sea trials | April 2028 |
None of this has gone to sea yet. Under the "Blue Harmony" project, the engine is due to be installed on a 17,500-deadweight-ton multipurpose vessel that a shipyard in Onomichi, Hiroshima Prefecture, is building for Mitsui O.S.K. Lines and its subsidiary MOL Drybulk. Installation is planned for January 2027. After the engine takes on hydrogen fuel from Kawasaki's onboard system and goes through sea trials, the actual-vessel demonstration voyages start in April 2028. The wait between a clean factory run in September 2026 and open-water demonstration in 2028 is where hydrogen combustion in shipping will be judged: fuel systems that hold up in a test bay still have to prove they can handle vibration, salt air and years of duty cycles on the multipurpose vessel.