I asked this question about a year ago with no answer so after spending all day today searching my boat for electrolysis, I thought I would share my experience for all to learn from. I thought since my engine and tranny is out of the boat, what better time to search for my electrical leak. I thought that with the prop shaft not touching anything but water, I can use that as a ground and search the boat with my multimeter for stray current. My multimeter is pretty sensitive (much like me) but also has a frayed wire (much like me 
) so I was picking up all kinds of very small volt readings all over the place. It was hard to tell which were real current and which were my old multimeter not working correctly. I tried my newer meter and it didn't show anything at all. I was just about to give up when I somehow ended up taking the negative wire off one battery bank and then connect the multimeter ground to that and walla...I got bigtime results...12.9 volts. I was happy and sad at the same time. So...I start checking the bus bars (common place to run ground wires) and they were all positive. I started disconnecting wires from the bus bars and most were positive even after disconnected. Next thing you know...I got wires disconnected all over the place including the windless and I still have 12.9 volts on the mast, shrowds, anchor, through hulls...you name it. I was going nuts. I finally was able to trace a positive black wire to the refrig which was re-wired this spring by an electricion....you guess it...it was wired wrong. BUT still have a positive mast and all others. Now I go back to the begenning and I pay real close attention to the 2 month old $600 charge. Seems that with only one wire connected (a red wire), all other 3 prongs had a positive charge including the ground prong. Damn...there's problem #2 but I still have 12.9 volts going through the mast. Now I'm going nuts...got got all the wires disconnected that go up the mast, all the wires to the speed and depth transducers disconnected and I still can't find it. I got all the bus bars disconnected too so I go back to step 1 (trace the positive flow). I keep the multimeter on the mast and I just follow the positive flow off the battery disconnection it along the way at each connection. Hey...what do you know. I found it. It's the damn bilge pump. After disconnection the bilge pump the multimeter goes to zero. I check all through hulls and the shrowds and anchor and promp and everything is zero. I trace the bilge pump wire and see it goes a few places and just as I get about halfway, the sun goes down and it got dark and I have everything disconnected. So now that I type on my laptop with an hour left of battery time, I'm thankful that I have two more days to fix this problems and get it all back together before I have to go to work. I sure hope I remember how to put it all back together and I haven't lost any screws and nuts (from the boat, not my head) SO HOW DO YOU TROUBLESHOOT? 1) disconnect one battery bank totally (pos and neg). 2) disconnect the neg from the battery (on the battery bank to test first). 3) get a nice long wire with two clamps on each end with a regular multimeter and connect one end of that wire to the neg post on the battery and the other end to the neg wire on the multimeter. 4) go around and check for volts in the ground system on the boat, including the mast, through hulls, and shrowds. If you found a volt reading on any of this stuff, you have an electrolsys problem and you need to find it by narrowing down the system by disconnecting the ground system into little systems. Once you narrow it down, start disconnecting positive wires to find the problem. 5) Repeat steps 1-4 for the other battery bank.
) so I was picking up all kinds of very small volt readings all over the place. It was hard to tell which were real current and which were my old multimeter not working correctly. I tried my newer meter and it didn't show anything at all. I was just about to give up when I somehow ended up taking the negative wire off one battery bank and then connect the multimeter ground to that and walla...I got bigtime results...12.9 volts. I was happy and sad at the same time. So...I start checking the bus bars (common place to run ground wires) and they were all positive. I started disconnecting wires from the bus bars and most were positive even after disconnected. Next thing you know...I got wires disconnected all over the place including the windless and I still have 12.9 volts on the mast, shrowds, anchor, through hulls...you name it. I was going nuts. I finally was able to trace a positive black wire to the refrig which was re-wired this spring by an electricion....you guess it...it was wired wrong. BUT still have a positive mast and all others. Now I go back to the begenning and I pay real close attention to the 2 month old $600 charge. Seems that with only one wire connected (a red wire), all other 3 prongs had a positive charge including the ground prong. Damn...there's problem #2 but I still have 12.9 volts going through the mast. Now I'm going nuts...got got all the wires disconnected that go up the mast, all the wires to the speed and depth transducers disconnected and I still can't find it. I got all the bus bars disconnected too so I go back to step 1 (trace the positive flow). I keep the multimeter on the mast and I just follow the positive flow off the battery disconnection it along the way at each connection. Hey...what do you know. I found it. It's the damn bilge pump. After disconnection the bilge pump the multimeter goes to zero. I check all through hulls and the shrowds and anchor and promp and everything is zero. I trace the bilge pump wire and see it goes a few places and just as I get about halfway, the sun goes down and it got dark and I have everything disconnected. So now that I type on my laptop with an hour left of battery time, I'm thankful that I have two more days to fix this problems and get it all back together before I have to go to work. I sure hope I remember how to put it all back together and I haven't lost any screws and nuts (from the boat, not my head) SO HOW DO YOU TROUBLESHOOT? 1) disconnect one battery bank totally (pos and neg). 2) disconnect the neg from the battery (on the battery bank to test first). 3) get a nice long wire with two clamps on each end with a regular multimeter and connect one end of that wire to the neg post on the battery and the other end to the neg wire on the multimeter. 4) go around and check for volts in the ground system on the boat, including the mast, through hulls, and shrowds. If you found a volt reading on any of this stuff, you have an electrolsys problem and you need to find it by narrowing down the system by disconnecting the ground system into little systems. Once you narrow it down, start disconnecting positive wires to find the problem. 5) Repeat steps 1-4 for the other battery bank.
