Join Date: Jul 2016
Location: British Columbia
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Re: 12V ground on the boat
A short postscript to my last post:
Reading a bit about sacrificial anodes and such made me realize that the voltage differential I was seeing between earth ground (via the keel) and the battery - terminal was in fact the process of corrosion underway on the zinc anode installed on Saturday when I did the anti-fouling paint on the hull and keel. The fluctuation in voltage I observed on the DVM was apparently a result of electrolysis occurring in the vicinity of the sacrificial anode and mediated by variations in the chemical composition of the sea water occurring in real-time as the process was underway and localized in that area. (This is not to say that there is no voltage potential difference between the battery -ive terminal and earth ground.) This explanation is perhaps not as clear as it could be, but I am necessarily temporizing here.
In any event, I realized that as the MD6B is raw water cooled, it would be foolish to insulate the engine from the keel and I therefore reconnected the keel-engine bond in order to include the motor in the sacrificial zinc anode system. In other words, the zinc anode on the keel will also protect the engine from internal corrosion by way of sea water in the water jacket, and hopefully also the sail drive.