U.S. imports of Marine Diesel & Semi-Diesel Compression-Ignition Piston Engines (HS 840810) totaled $23.5M in August 2026, imported from 19 countries.
Importers of Marine Diesel & Semi-Diesel Compression-Ignition Piston Engines paid $2.0M in duties in August 2026, an average duty rate of 8.21% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule. Marine Diesel & Semi-Diesel Compression-Ignition Piston Engines imports of $23.5M in August 2026 ran 30% above the year-to-date monthly average of $18.1M.
Last updated: August 2026 dataDiesel and semi-diesel engines for marine propulsion are classified under heading 840810, with seven 10-digit lines spanning a wide power range from below 111.9 kW (8408100005) through above 746 kW (8408100050) — a structure that reflects the enormous diversity of commercial marine applications from small workboats to large commercial vessels. Germany and Japan lead US imports under this heading, consistent with their dominant positions in commercial and recreational marine diesel manufacturing. High-power marine diesels above 373 kW are typically capital goods for commercial shipping or offshore applications, where lead times, warranty terms, and classification of spare parts are recurring compliance considerations.
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230 import shipments a month
CBP requires classification based on the manufacturer's rated continuous output in kilowatts as stated in the technical specification sheet. When output is near a boundary (e.g., close to 149.2 kW or 373 kW), importers should use the certified rated power from the type-approval documentation rather than nominal or peak figures. Obtaining a binding ruling from CBP is advisable for high-value engines where the correct line is genuinely uncertain.
Yes. Marine diesel engines above certain power thresholds are subject to EPA Tier standards for marine compression-ignition engines under the Clean Air Act. Importers must verify that the engine model holds a valid EPA certificate of conformity for the applicable tier before entry; non-certified engines may be detained or refused admission. This requirement applies independently of CBP tariff classification.
Subheading 3 of 3 in heading 8408
Subheading 840810 · $23.5M of $463.6M
ImportsExports
Imports
$23.5MYoY · free account
Exports
$19.7MYoY · free account
12-mo low · imports
Low · free accountOver the twelve months to August 2026, the U.S. imported $208.9M of Marine Diesel & Semi-Diesel Compression-Ignition Piston Engines and exported $218.9M.
Through August 2026. Source: U.S. Census Bureau.
Trade Directory
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HS10 import codes under this HS6 parent, each with its own page. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Imports for consumption | Average duty rate | Dutiable Share | Duty Collected |
|---|---|---|---|---|---|
| 8408100050 | Comp-Ignition Piston Engines, For Marine, Exc 746 Kw | $14.8M | 7.79% | 74.58% | $1.2M |
| 8408100030 | Comp-Igni Pst Eng, Marine, Exc223.8kw, Not Exc 373 Kw | $4.6M | 9.12% | 87.22% | $419K |
| 8408100040 | Comp-Igni Pst Eng, Marine, Exc 373 Kw, Not Exc 746 Kw | $2.1M | 10.54% | 100.00% | $218K |
| 8408100020 | Comp-Igni Pst Eng, Marine, Exc149.2kw, Not Exc223.8kw | $1.5M | 6.95% | 69.34% | $108K |
| 8408100005 | Comp-Ignition Piston Eng, Marine Prop, N/Exc111.9kw | $576K | 6.43% | 51.88% | $37K |
| 8408100015 | Comp-Igni Pst Eng, Marine, Exc111.9kw N/Exc 149.2 Kw | $164K | 10.00% | 100.00% | $16K |
HS10 export codes under this HS6 parent, each with its own page. Source: U.S. Schedule B export classification.
Import lines come from the U.S. Harmonized Tariff Schedule and export lines from Schedule B. The two are numbered by different agencies, so the same 10-digit code can appear in both tables describing a different product.
Imports · August 2026
origin
Germany and Sweden together supply 69% of it. Japan pays 12.5% duty; Denmark 0.0%.
customs district
destination
entry
rate provision · imports
19.3% enters free of duty; duty collected equals 8.21% of imports for consumption.