Under EPA s definition, an engine is considered new until its legal or equitable title has been transferred, or the engine has been placed into service. Starting with the implementation dates of the new emission standards, EPA will consider vessels new until their equitable or legal title has been transferred to an ultimate purchaser. In addition, EPA will consider a vessel new if it undergoes such modifications that the modified vessel derives at least half of its value from new materials or components. This latter provision is intended specifically to prevent someone from re-using the hull or other parts from a used vessel to avoid emission standards. With few exceptions, the rule applies equally to propulsion and auxiliary engines.
Drill ships are clearly marine vessels, so engines installed in drill ships are marine engines.
A third class of drilling equipment is less clear. Semi-submersible drilling rigs are moored to the ocean bottom, but have some propulsion capability. We consider these to be marine vessels, so any engine that is installed on such a rig would be a marine engine. EPA has established a provision for exempting foreign trade vessels from the standards.