Originally Posted by espresso
this topic of grounding the Aluminium hull
is such a debated point, but the way it was explained to me was:
1) It is almost impossible in real situations to keep the hull
insulated from the battery
. Just a touch of dirt on the engine
mounts, graphite brush dirt from the alternators, temperature or pressure senders can connect the hull to the battery
I guess we have to agree to disagree about the best electrical
treatment for aluminium hulls.
I think however you have misunderstood how to isolate the negative supply. This is not normally dependent on the engine
mounts, a simple solenoid that only connects the negative to the engine during start is simple, cheap
and reasonably foolproof. Likewise 2 wire senders are fairly readily available.
Many aluminium yachts, like mine, ( and for example all Ovni's) have a test for negative isolation that permits easy frequent checks that the isolation is effective.