My understanding is that if the boat is not “for hire”…in other words, you’re not carrying people or cargo for money, you don’t need a license. If the owner decides to charter the boat, as in people paying him for the boat and him paying you to run it, I believe you’ll need a 500 ton ticket. And if that’s the case, in addition, you’ll need full STCW certification to run it past near coastal waters, i.e. outside of 200 miles.
You’ll have to check the specific country’s regs to be sure over there.
I’m certainly no authority on these matters, but there are people on this board that are. Somebody will come in with good information. They always do…usually to correct ME!:o I don’t mind a bit. I take direction well.