MARPOL Annex VI Regulation 13, MEPC.398(83), Tier I/II/III Limits, Onboard Test Cycle, SCR/EGR Gap, EIAPP & Retrofit Economics

Marine Engine Substantial Modification, NOx Tier Re-Certification & Retrofit Cost Tool

Screen whether an engine change is routine maintenance, a substantial modification, a more-than-10% MCR uprating, a replacement-engine major conversion or a voluntary higher-Tier certification. Calculate the applicable NOx Tier limit from rated speed, compare weighted engine-cycle emissions, size the required NOx reduction, test SCR / EGR / tuning performance, estimate reductant and fuel penalties, build the onboard certification budget, check the new 1 September 2026 section 7.2 test-plan requirements, and expose the real commercial cost of re-certifying an installed marine diesel engine.

Currency
Currency selector changes display only. No exchange-rate conversion is performed.

Engine & Ship Certification Basis

kW after the proposed modification.
kW on original EIAPP / Technical File.
rpm after proposed modification.

Proposed Modification / Certification Route

Choose the closest regulatory path. The tool separates substantial modification from the independent MARPOL major-conversion trigger created by an MCR increase greater than 10%.

For engines on ships constructed before 1 Jan 2000, substantial modification depends on measured emission-characteristic increase beyond the Code allowance.
Use override for Norwegian Sea contract / keel / delivery date rules.
MEPC.398(83) section 7.2 allows Individual Engine or Engine Group, not Engine Family.

Simple NOx Emission & Retrofit Performance

g/kWh, measured or defensible certified / test estimate.
% weighted reduction relative to baseline.
g/kWh. 0 = baseline × (1 - reduction).
% of rated power available during section 7.2 onboard test.
mbar increase.
mbar from engine / turbocharger maker.

Advanced NOx Test-Cycle Register

The cycle and weighting factors follow MARPOL Annex VI Appendix II. Enter representative pre-retrofit NOx and load-point-specific reduction. The calculator reports the total weighted cycle value.

PointSpeed %Power / torque %WeightBaseline NOx g/kWhReduction %Post NOx g/kWhWeighted post

Operating Exposure & Retrofit OPEX

% MCR.
Hours the selected retrofit is expected to operate in compliance mode.
g/kWh.
%. Positive = penalty, negative = saving.
Selected currency/tonne.
kg solution/kg NOx removed. Editable project assumption.
Selected currency/tonne solution.
Optional value of access, charter premium or avoided alternative solution.

Retrofit, Testing & Re-Certification CAPEX

days.
Selected currency/day.
% of equipment + installation + engineering + certification + testing + trial cost.

1 September 2026 Section 7.2 Readiness

NOx certification screening only: This tool is not an Administration decision, EIAPP certificate, approved Technical File, engine-family / engine-group approval, test-bed certification, onboard NOx measurement plan, SCR Scheme A/B approval, engine-room integration study, transient backpressure analysis or proof that a modification is legally "substantial." Final applicability and certification route depend on the flag Administration / Recognized Organization, original engine certification, current NOx Technical Code version, approved components, ECA applicability and the exact modification scope.
Current regulatory basis: Resolution MEPC.398(83) enters into force on 1 September 2026 and adds NOx Technical Code section 7.2 for an installed engine subject to substantial modification or being certified to a Tier it did not hold at installation. The section allows Individual Engine or Engine Group certification, not Engine Family certification; requires an Administration-agreed Engine Emission test plan; requires a changed nameplate where rated power and/or speed changes; and permits the nominal 100% test-cycle point to be no lower than 85% of rated power subject to the agreed test plan. IMO Regulation 13 Tier limits remain speed-dependent. The 2025 SCR Guidelines adopted by MEPC.399(83) update the certification framework for SCR-equipped marine diesel engines. IMO Regulation 13 · IMO MARPOL Annex VI resolutions
Generated by ShipUniverse.com
By the ShipUniverse Editorial Team — About Us | Contact