Jeff: weigh in on the question of a change in Capac reading when boater plugs into shore power. I used to know this stuff but it escapes me. Shore power is AC and shouldn't affect CAPAC which is reading DC potential. If there is AC grounding/short issue should that bleed over into hull stuff??
And on the range question, I used to run at .6 (brackish water - partly salty/partly fresh) and at first it scared me but I didn't see any corrosion and learned to live with it. Your mileage though may vary
Shore power should NOT change the CAPAC readings. If it does, there's something wrong with your isolation unit (and that needs to be corrected).
"We live at the bottom of an ocean of air, not at the top." General Marvage Slatington