We do have some good discussion on this in the archives
. But it is a case of are they easy to find.
There are two schools of thought. Isolate everything and connect everything. Both have advantages and disadvantages. I lean toward the connect everything class. If you connect everything, you can not have current
flow between as there is a short. The anode takes care of the "whole".
The isolate class consider, if you isolate then current
can not flow because there is nothing to connect them. Where that falls down is when you have something that is slightly conductive connecting them. As in, maybe there is enough conductivity in a timber hull, or the plumbing
to the enigne or what ever. But also the same thing can happen if you do not have a conductor of sufficient capacity to carry the very small current that flows. This can happen by resistance in either the cable itself, or in any connection to a fitting.
What I assume may have happened in your case is, the bolt has corroded enough to then reduce its conductive ability to the fitting. Thus the bolt then becomes seperated from the circuit protection. But as the anode is protecting all the other fittings, the voltage potential is different between the screen
and the bolt. Enough resistance is between the bolt and fitting via the hull. The saltwater connects the otherside and away if goes.
The remedy is to ensure the new bolt has a good clean contact to the screen
fitting. Maybe even place a small amount of sealant
over the cap of the bolt to help keep water
Umm, I do assume the bolt was bronze as was the screen being bronze. If the two are dissimilar metal in anyway, it will cause the same action.