Hi Ray, although you look as though you have the answers you need for now. You may be interested in some light youtube vlogs to give a better understanding of boat electrics
"cruising the cut" this is journalist living on a narrowboat, a good starter for electrics.
"journey with jono" still a narrowboat but more techi.
But the best vlog for me is a guy called "greg virgoe" he`s converting a merc sprinter van into a motorhome.It gives advice on planning,mains,12 volts,power audits,solar panel,cable sizing and lots more.Although its got a bilge pump and nav light or two missing its still relevant for boat use. Enjoy if you can stay awake