Engine test requirements for
amended NOx Technical Code
| Applicability: Ship operators, ship managers, ship masters, shipbuilders, ship manufactures and ship agents. |
The International Maritime Organisation’s MEPC 83 (April 2025) adopted a number of amendments to the NOx Technical Code 2008 in Resolution MEPC.398(83). They include Parent Engine test requirements for a marine diesel engine. |
Applicability of amendments
These amendments apply to any marine diesel engine that undergoes a substantial modification or is to be certified to a NOx Tier to which it was not previously certified, so requiring re-certification. Although these changes enter into force on 1 September 2026, the MEPC has invited their early application as they do not alter any existing requirements and help to mitigate risks and ensure continued compliance.
Engine test requirements
The majority of the NOx certification will continue to be based on test-bed testing, which is reflected in the existing engine test requirements. However, for an existing, installed engine subject to substantial modification, or which the owner/operator now requires to be additionally certified to NOx Tier III, there will not be, in most cases, a comparable engine available for that test-bed testing.
Consequently, these NOx Technical Code amendments provide some flexibility regarding aspects of the NOx certification Parent Engine test requirements. They will allow for that testing to be undertaken on an installed engine without affecting the overall rigour of the process. Therefore, following such testing, a new Engine Group will be established in this case and other so altered comparable engines could then be certified as Member Engines following the usual procedures without requiring emission measurements.
What shipowners and operators should do now
Please note these amendments and act as necessary regarding their possible impact on your operations, certifications and crew training.
For further information
Resolution MEPC.398(83) contains the complete documentation for the amendments. If you would like more details or need support with these requirements, please contact technicalexperts@lr.org.
