We were told by the harbor police here in so cal that if you want to not register the tender to a yacht it must have T/T "documentation number of mother ship" to ne legal.
In nearly every state I know of it's a no go. A dinghy
with a motor
needs full registration
. US Documentation
does not in any way shape of form extend to a dinghy according to the USCG. It then falls to the state laws (or country) where the dinghy is LOCATED not where you claim to be from.
The dinghy is just another boat in the water
. Without an engine
on the dinghy I know of no place that requires anything so how you label the dinghy is not an issue. In some places there may be a state sticker required even if they don't require numbers. You still need the proper lights at night and a hand held light may pass. PFD's and the rest of the usual gear