Wayne.B wrote in
:

Is it possible to install the isolator external to the boat using the
right combination of connectors and junction boxes?

T

Sure. Buy the 30A or 50A isolation transformer he
http://www.charlesindustries.com/main/ma_iso_bost.html

Mount it in a ventilated NMEA enclosure next to the dock power pedestal so
it can cool itself. Run a short cable from the transformer to plug into
the dock pedestal, then, with the appropriate AC twistlock outlet for the
size of the transformer mounted on the outside of the NMEA box, plug the
boat into the box....KEEPING THE BOAT GROUND DISCONNECTED FROM THE DOCK
GROUND, PLEASE!

Both sides of the isolation transformer are isolated from ground. There is
no grounded neutral like shore power uses. The only way you can be shocked
is when you are directly connected ACROSS L1 and L2 on the transformer
secondary. That's why they call it "Isolated" in the first place.

Unconnected from dock ground and the grounded nonsense of the marina and
rest of the halfass-wired boats, your galvanic current ashore is zero,
leaving only galvanic currents caused by your boat eating the zincs.