Extreme Corrosion Problem - see attached pics

[fenster]

When I pulled my 1991 Chris Craft out of the water last season, I found the entire lower unit was totally corroded. <br /><br />Upon further investigation, I found the marina had mistakenly hooked up the AC ground wire to the postive terminal on my battery.<br /><br />From what I can gather, whenever I used my battery, the current flowed from the negative terminal through my boat and rather than back into the battery through the positive terminal, it went through the ground wire and through the lower unit, corroding it. <br /><br />Would this also explain why my battery kept dying last season and the marina recommended I hook it up to the ship-to-shore and run the battery charger when it was docked?<br /><br />Can any one verify this theory? Here are some pics showing the incorrect hookup and corrosion damage. <br /><br />Incorrect hookup (green ground to positive terminal) <br />

<br /><br />Lower Unit<br />

<br /><br />Any input or theories would be appreciated!<br />-Adam

 

[Buttanic]

Re: Extreme Corrosion Problem - see attached pics

If the marina connected the ground wire I say they owe you a new outdrive. 110 VAC should never be tied into the 12 VDC system.

 

[jlinder]

Re: Extreme Corrosion Problem - see attached pics

WOW !!!<br /><br />Not sure the AC ground to batt positive was the problem, but is sounds pretty likely. The water would be at ground potential by the AC ground, and the outdrive would be negative 12 volts because of the battery. This would cause a constant current through the metal. I would want people with more knowledge to confirm this though.<br /><br />I would document everything and want the marina to pay for the damage.<br /><br />You don't show the anodes. Are they still there, or worn out?<br /><br />Also, if your battery was continually drying out is a problem. It sounds like it was overcharging. The battery may have been damaged.

 

[18rabbit]

Re: Extreme Corrosion Problem - see attached pics

Welcome to the board. I wish you could have joined under more positive circumstances.<br /><br />Thanks for posting pics with your query. It’s helpful, worth 1000 words. Unfortunately, I’m guessing you are going to have to eat the cost of this. I am making presumptions based on the pic of the battery. I’m thinking there is something more going on with your boat that you haven’t told us.<br /><br />I am looking at three identical crimped connectors. One goes to the green wire the marina ‘accidentally” installed. Did the marina also “accidentally” install two red wires? Whoever did the electrical work on your boat didn’t get it quite right. And I don’t like the color of yellow that I see. Yellow is ok for AWG 12, the min size the green wire has be, but those look like common automotive ring connectors, not marine grade. It looks like corrosion is already starting on the end of the green wire so I am presuming it is not tinned, and in the dimple on the ring terminal of the red wire on the right. I could be wrong, maybe just pixel aberration characteristics of your camera.<br /><br />I also question a marina’s involvement in hooking up anything electrical on a boat, especial anything to do with shore power that does not go thru appropriate shore power connectors.<br /><br />Depending on what’s going on with your boat’s electrical, that green wire could very well provide a path for 12vdc from your bat’s positive post, thru your lower unit, and into the water. If that is the case, your boat was likely a source for other boats’ galvanic corrosion issues in that marina. Where does the other end of that green wire go? What is it connected to?<br /><br />Fwiw, the ac ground (green wire) is supposed to be a direct path to ground, not a source of ac current. If you have an inverter onboard, it is possible the green wire is tied to a common ground (ac and dc) and you would have a direct short between battery posts, tho I would have expected more fireworks unless you have (or used to have due to corrosion) a common connection at a ground plate below the waterline. So I presume separate ac and dc grounds.<br /><br />As shown in your pic, IF the marina’s shore power continuity is correct, the result would be a dead battery every time you hooked up to shore power.<br /><br />You have two problems, (1) a dead lower unit, and (2) mucked up electrical onboard. If the marina actually connected that green wire, I suggest you hire a certified marine electrician to document everything about that. You’ll need it to pursue compensation from the marina.<br /><br />As far as fixing the electrical, there are several people on this board that can help you correct that if you are marginally handy and want to go down that road. Just don’t inquire about crimping vs soldering too early on.