This regulation follows an earlier proposed marine engine rule which was published in December, 1998. The scope of application of the marine engine rule covers all new marine diesel engines at or above 37 kW, including both propulsion and auxiliary marine diesel engines. Auxiliary engines are all other marine engines. Classification of drilling rigs depends on their propulsion capability.
Drilling ships are considered marine vessels, so their engines are subject to the marine rule.
Semi-submersible drilling rigs which are moored to the ocean bottom, but have some propulsion capability, are also considered marine vessels. In contrast, permanently anchored drilling platforms are not considered marine vessels, so none of the engines associated with one of these facilities are marine engine. Consistently with the land-based nonroad regulation, a portable auxiliary engine that is used onboard a marine vessel is not considered to be a marine engine. To distinguish a marine auxiliary engine installed on a marine vessel from a land-based portable auxiliary engine used on a marine vessel, EPA specified in that rulemaking that an auxiliary engine is installed on a marine vessel if its fuel, cooling, or exhaust system are an integral part of the vessel or require special mounting hardware. All other auxiliary engines are considered to be portable and therefore land-based.