Whatever your original project was that got you asking this question
(I would like to know that answer also), your single minded priority
now should be either

1) finding a qualified electrician to take over the original project,
or who will at the very least evaulate your boat before you next plug
back into shore power. Such an evaluation can only be successful if
you labeled all the wires as recommended in this thread, and such
qualified electrican tests your work with a meter and inspects each
area you stated you modified.

2) if your not going to do #1 above, then identifying and
disconnecting the place in the boat where nuetral and ground are
connected together and undoing must override anything else your
thinking about doing next. You cannot reliable trace the wires, and it
is commonly recognized as bad wiring practice to have them connected.

3) If even better than #2, just stop and don't do anything if you
cannot do #1. If this project does not kill you, it could kill a
future visitor to your boat if the ground protection isn't working,
could kill someone in the water near your boat while it is plugged
into shore power, and can bring with it numerous problems of stray
current to your boat or those nearby.