"w_tom" wrote in message
ups.com...
All major components on a boat should be electrically bonded
together. This is especially important to human safety. Your gas tank
is electrically floating? Then it is a situtatoin similar to what
destroyed a 707 over Elkton MD. That is dangerous. Gas tank should
be grounded using a 10 AWG (or heavier) ground wire so that engine,
tank, and all other major metal components are bonded electrically and
so that bonding makes a connection to water.

A discussion of this concept:
http://www.thomson.ece.ufl.edu/lightning/ Summary
http://www.thomson.ece.ufl.edu/lightning/IEEE.pdf IEEE paper
http://www.thomson.ece.ufl.edu/lightning/video.html Video



Apparently there are some exceptions to what is bonded and what is not. My
boat is equipped with Volvo diesels and Volvo purposely does not bond the
engine, shaft and props to the boat's common bonding system. The reason is
to reduce electrolysis due to DC leakage.

I found this out when the boat was modified with thrusters. The installer
connected the thruster housings and motors to dedicated batteries that where
also connected to the main batteries for charging. He also connected the
thruster motors to the bonding system. It was discovered during regular
in-water hull cleaning by the diver who noticed "tingling" when he touched
the shafts or props. Disconnecting shore power plus a host of other
experiments did not get rid of the tingle, which was very mild, BTW ... he
could feel it if he brushed a shaft or prop with the back of his hand.

A call to Volvo provided the explanation of why the engines and shafts were
not bonded. I disconnected the thruster batteries from the mains and the
"tingling" went away. Ended up installing a separate, dedicated charging
system for the thruster batteries.

All bronze thru fittings, etc. are bonded. Interestingly, the electronics
(radar, etc.) is obviously grounded to the batteries via the DC power
return, but they are *not* bonded.

So, on my boat, red is 12vdc positive, black is 12vdc negative and green is
bond.

Eisboch