LOts of us are husband/wife teams. You really should have a "Change of control" document. Assuming the very worst happens, the party listed on the ships papers becomes incapacitated or dies. The survivor sails
Some places the boat will not be allowed to leave, nor can the survivor so anything with the boat (sell f.eks), until the estate is settled.
A simple notarized document (or witnessed) saying something like:
In the event of my incapacitation or death, XXX assumes the position of Captain
with all the rights and privileges association with that position, including, but not limited to, sailing the boat onwards to any destination
, transfer of the boat to any destination
by any chosen 3rd party, sale
of the boat.
That's pretty clear language and will allow the survivor to retain control of the boat.