Marine engine
Marine engine means a nonroad engine that is installed or intended to be installed on a marine vessel. This includes a portable auxiliary marine engine only if its fueling, cooling, or exhaust system is an integral part of the vessel. A fueling system is considered integral to the vessel only if one or more essential elements are permanently affixed to the vessel. There are two kinds of marine engines:
(1) Propulsion marine engine means a marine engine that moves a vessel through the water or directs the vessel's movement.
(2) Auxiliary marine engine means a marine engine not used for propulsion.
Source
40 CFR § 1042.901
Scoping language
The following definitions apply to this part. The definitions apply to all subparts unless we note otherwise. All undefined terms have the meaning the Clean Air Act gives to them. The definitions follow: