Hi
Name you boat what ever you want. Yes two boats can have the same name. Your rego is how RMS track you for rego payments. Marine Rescue track me by my call sign CC796. I think when I sign up with the App, my boats name (StressFree) is in the photo and its in the marine rescue app as the name of my "Profile" in case you have more than boat. I have heard people use their boats name when they call up for radio checks. In my case, I'd use my call sign. I guess if you are using VHF, then you need a call sign, although I'm not 100% sure about that.
@frankS Love the name Nimrod!
@M1100S what is your new boat?