47 CFR 80.1181: Station identification.

(a) On-board stations must identify when:

(1) The vessel is within 32 km (20 miles) of any coastline; or

(2) The communications are likely to be received aboard another vessel.

(b) Identification, when required, must be:

(1) Transmitted at the beginning and the end of a series of communications. Whenever communications are sustained for a period exceeding 15 minutes, station identification must be transmitted at intervals not exceeding 15 minutes.

(2) In English and must include the name of the vessel, followed by a number or name designating the respective mobile unit, for example: “S.S. United States Mobile One, this is Mobile Two.”