Re: MMSI into Icom IC-M504
There are two different issues here.
The first is the MMSI number differences between a Boat U.S.-issued one and one issued by the FCC. The first type is not entered into the ITU international database and thus is not available to, e.g., foreign search-and-rescue entities.
I know of no specific prohibition to a boat with a Boat U.S. - issued MMSI communicating by voice with a foreign vessel.
HOWEVER, there is a prohibition of communicating with foreign vessels or in other countries without having two things:
1. a commercial radiotelephone Operator's Permit; and
3. a Station Lcense for the boat.
Both of these (the Permit and the License) are issued by the FCC upon application. Along with their issuance, you automatically are assigned a MMSI number, and this number should be used in your VHF, HF, AIS, etc.
So, strictly speaking, if you're off Cove Point in the Chesapeake and want to talk with a foreign-flagged LPG carrier via VHF you need to have the FCC-issued operators permit and station license.
At least that's the way I understand things.
Bill has it correct, and you would find language about this on the application form for the radio license. However, as always, in an emergency, all bets are off and it is ok.
Having said this though, I know that US flagged boats frequently communicate with the commercial vessels, most of whom are foreign flagged, and with the occassional visitor migrating south. It hasn't been enforced.