I am aware of the reccomendations for lightning and SSB grounding
systems but I believe those are separate from the DC system ground. In
books I have read about the DC electrical system ground at the engine
refered to as a polarizing ground. Exactly what a polarizing ground
does or why it is desireable, is not explained. This from the USCG
regs:

Sec. 120.378 Ungrounded systems.

Each ungrounded system must be provided with a suitably sensitive
ground detection system, located at the respective switchboard, that
provides continuous indication of circuit status to ground with a
provision to momentarily remove the indicating device from the
reference
ground.

So what is a "suitably sensitive ground detection system"?

I am also aware of the plastic thru-hull wood hull issue but that is
for another forum. A properly installed plastic thru-hull in certain
wood hulls is not a problem.

fritz



"Rusty O" wrote in message hlink.net...
Lightning protection systems and marine SSB radio systems need a direct
connection to the sea water. DC electrical power systems do not need a
connection to the water. Just use a common grounding point for the negative
side of the battery (or batteries) and the negative leads from your
electrical loads. Blue Sea makes some nice ones with large bolts for the
battery leads and smaller screws for the various loads. You could also creat
your own from a strip of copper plate and either use bolts and nuts or
threaded holes for the connections. Some MaryKate Tek Gel assembly lube will
help protect against corrosion.

By the way, plastic thru-hulls fittings are not recommended for wood hulls.
The expansion and contraction can crack them. You really should use bronze.
That advice also applies to thru-hulls for speed and depth transducers.

Rusty O