U.S. flag? HF/MF
gear aboard? You need at a minimum a Restricted
Marine Radiotelephone Operator
Permit, as well as your FCC Ship Station License. Get your MMSI with the Ship Station License. You should then be good to go practically anywhere in the world.
No test for either license. Go online, fill out the forms, pay with your cc and your licenses come to you in the mail. Program your new
AIS,
EPIRB, VHF, etc with your new MMSI and you're done.
You would be well advised to go for the (unrestricted) MROP license, or General Radiotelephone License (GROL) simply because in studying for the exam, you will probably actually learn a thing or two. You are not above the law just because you are ignorant of it. Learn what is
legal and not, what is possible and not, what works and not. The test for GROL is actually pretty involved and you will learn quite a bit about how radio actually works, and basic troubleshooting techniques. Sort of like going for your General class HAM license. Or maybe Advanced class. I don't know... they kind of dumbed down the HAM requirements. Anyway, a higher class license means you had to at least memorize some useful information. The Restricted MROP license only means you know how to fill out a form. But you are still responsible for illegal transmissions, etc. The GROL is a lifetime license. I got that and also 2nd Class Radiotelegraph and Ship's
Radar Endorsement. Don't have a ham ticket anymore. Got tired of the junk mail and I strongly disagreed with dumbing down the Morse requirements. But speaking of which, you might find a HAM license useful to you. Your Ham license is both operator and station license. As a general
rule, you can operate ham gear on the ham bands under the authority of your US license while at sea on your boat. Most Ham transcievers have full coverage
reception so you can listen to
marine safety broadcasts,
weather forecasts, etc and even pull WEFAX, RTTY, CW, and other digital modes. It is generally NOT
legal to transmit on marine bands with ham
equipment. It is NOT legal to modify marine HF/MF
SSB equipment for transmitting on the Ham bands. Well, actually it is only illegal to transmit on Marine bands with equipment you have modified, not to modify it per se. There are radios type accepted for both services, though. Anyway you might consider getting both types of license.
For Marine VHF operation, you need to be licensed when in most countries' waters. Once again, your Restricted MROP will be a minimum requirement. Even though you no longer need a license in U.S. waters, you will need it overseas. And your MMSI must be one assigned by the FCC and not by a third party.
Bottom line: as a minimum, get your Restricted MROP and a Ship Station License.