basskisser wrote:
K Smith wrote in message ...

CCred68046 wrote:

I have seen this grounding questions with metal boats before and I dont
understand what the issue is. If the boat has a motor I can almost guarentee
its grounded somewhere to the hull weather its inboard or outboard. Would
someone actually go through the trouble and expense to isolate the electrical
system from the hull? That would take a lot to do!!

The debate is long & I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.


How can an electrical circuit be made if there isn't any ground?

It's as expected, by a second wire going back to earth.

Say alternators there is only two connections to the alternator case &
therefore the engine block itself?? The fields are usually controlled by
the regulator earthing them back to the negative side of the battery via
the case/block & earth strap, insulate the second slip ring bush from
the case (the same as one is already) & include an extra light earth
wire so now the fields are still "earthed" to the battery but you've cut
the case/block etc out of the circuit & obviously you no longer have an
earth strap from the battery to the block.

Likewise the starter, it's only convenience that they don't require two
wires,& again it's only because one set of starter motor brushes are
earthed to the starter case that current can get to the block, insulate
then as the delivery set of brushes already are & then the case is above
ground. You then need an earth strap direct to a terminal on the starter
instead of the engine block.

Most larger proper marine diesels have all their electrics above ground
with specific earths included in their wiring. Given spark engines are
not really "proper" :-) marine engines, we're unaware of any that have
such a system.

The biggest problem is leaking currents to the block & hence the
stainless prop shaft with a bronze prop attached, bad enough but add a
steel hull & .........



K