40 CFR 1045.5: Which engines are excluded from this part's requirements?

(a) Auxiliary engines. The exhaust emission standards of this part do not apply to auxiliary marine engines. See 40 CFR part 90, 1048, or 1054 for the exhaust emission standards that apply. Evaporative emission standards apply as specified in § 1045.112.

(b) Hobby engines and vessels. This part does not apply with respect to reduced-scale models of vessels that are not capable of transporting a person.

(c) Large natural gas engines. Propulsion marine engines powered by natural gas with maximum engine power at or above 250 kW are deemed to be compression-ignition engines. These engines are therefore subject to all the requirements of 40 CFR part 1042 instead of this part even if they would otherwise meet the definition of “spark-ignition” in § 1045.801.