Let me give it shot, gator clamps at both ends for easy connect, from the batterie ground post at one end to whatever ground system you are testing,then use your multimeter to read your voltage, if your voltage is the same without the the bipass wire your ground is good, might not be the right way of doing it but seems to work for me, also do the same for pos wire, that way you eliminate one system at the time.your first step would be to make sure your main ground is grounded to the hull properly, assuming you have a grounding block on the hull, mine is grounded to a true hull valve in the bilge area, not sure if it make sense???