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Electronic Code of Federal Regulations

e-CFR Data is current as of April 14, 2014

Title 40: Protection of Environment
Subpart B—Emission Standards and Certification Provisions

§91.104   Exhaust emission standards for outboard and personal watercraft engines.

(a) New marine spark-ignition outboard and personal watercraft engines for use in the U.S. must meet the following exhaust emission standards for HC+NOX. The exhaust emission standard for each model year is provided below. It is also used as input to the calculation procedure in §91.207 to determine compliance with the corporate average HC+NOX exhaust emission standard.

Hydrocarbon Plus Oxides of Nitrogen Exhaust Emission Standards

[grams per kilowatt-hour]

Model year P <4.3 kW HC+NOX emission standard by model year P >4.3 kW HC+NOX emission standard by model year
1998278.00(0.917 × (151 + 557/P0.9)) + 2.44
1999253.00(0.833 × (151 + 557/P0.9)) + 2.89
2000228.00(0.750 × (151 + 557/P0.9)) + 3.33
2001204.00(0.667 × (151 + 557/P0.9)) + 3.78
2002179.00(0.583 × (151 + 557/P0.9)) + 4.22
2003155.00(0.500 × (151 + 557/P0.9)) + 4.67
2004130.00(0.417 × (151 + 557/P0.9)) + 5.11
2005105.00(0.333 × (151 + 557/P0.9)) + 5.56
2006 and later  81.00(0.250 × (151 + 557/P0.9)) + 6.00


P = the average power of an engine family in kW (sales weighted). The power of each configuration is the rated output in kilowatts as determined by SAE J1228. This procedure has been incorporated by reference. See §91.6.

(b) Exhaust emissions are measured using the procedures set forth in subpart E of this part.

(c) Manufacturers must designate a Family Emission Limit (FEL) for HC+NOX for every engine family. The FEL may be equal to the emission standard in paragraph (a) of this section. The FEL established through certification serves as the emission standard for the engine family and emissions may not exceed the FEL levels for HC+NOX for all engines sold in the engine family, for their useful life.

(d) A manufacturer must comply with a corporate average HC+NOX emission standard as determined in accordance with subpart C §91.207.

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