Section 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 .