46 CFR §13.503

1. (a)Each applicant for a Tank Vessel-Engineer endorsement must provide evidence of at least—
   1. (1)90 days of service as an engineering officer on tankships or self-propelled tank vessels certified to carry DL or LG appropriate to the endorsement applied for;
   2. (2)90 days of rating or cadet service in the engine department on tankships or self-propelled tank vessels certified to carry DL or LG appropriate to the endorsement applied for; or
   3. (3)A combination of the service in paragraphs (a) (1) and (2) of this section.
2. (b)Each applicant already holding an MMC endorsed as Tank Vessel-Engineer for DL and seeking an endorsement for LG, or the converse, must prove at least half the service required by paragraph (a) of this section.