Larry, I think your conclusions are based on some incorrect assumptions
regarding the path resistances through earth and water.

The beginning point of disagreement may be your assertion that seawater
is a great conductor. Compared to copper, seawater is a terrible
conductor: orders of magnitude worse, in fact. I admit it is not easy to
do actual calculations on the resistance of a particular seawater path
using specific electrodes, since path resistance will depend on surface
areas of the electrodes and the distance between them, in addition to
the resistivity or conductivity of the seawater. But the concept should
be clear.

At 120 volts, a 50 ampere circuit would require a path resistance of 2.4
ohms. There is no way you can find a six foot path from your prop to the
earth below back to the ground/neutral AC connection point with a
resistance of 2.4 ohms. Even if the water path resistance were zero
ohms, (which would be low by some orders of magnitude) the earth itself
will constitute more than 2.4 ohms resistance. I would not advise you to
do this with 120 volts, but with a 6 volt transformer, connect one side
to your prop and the other side to your green AC grounding conductor and
measure the current and calculate the resistance of the path. The path
will be from the transformer to your prop through the water to the earth
through the earth to the ground/neutral connection point and then back
to your transformer through the green grounding conductor. Tell us what
you find.

So even if the path resistance through the water from your prop to the
prop in the next slip is an order of magnitude greater (quite unlikely)
than the path resistance from his prop back through the earth to the
ground/neutral connection point, there will still be a voltage between
your prop and green grounding wire on your boat (which has negligible
resistance back to the ground/neutral connection point). It is quite
possible that the path through your prop and green grounding wire will
have lower resistance than the path from the neighbor's prop through the
water and the earth.

Bottom line: what you have is an AC voltage connected to two parallel
resistances. But the key point is that these resistances are
sufficiently high that when a human body's resistance is added in
parallel with them, enough current will flow through the body to cause
electrocution.

FWIW, I think you are attempting to apply electrostatics principles to
this situation. It is quite true that if you have an object with a net
positive or negative charge and touch it to earth (or water) that net
charge will dissipate through the earth (or water). That simply doesn't
happen here. If you apply a voltage to two electrodes stuck in the earth
(or the water) you will find that depending on the parameters mentioned
above, a finite resistance is encountered. Place the human body's
resistance in parallel with that resistance and some current will flow
through the body. Not telling you a thing here, Larry, just that the
issue is really the magnitudes of the path resistances involved. Even at
RF, seawater does not offer anything close to a zero ground loss
resistance. Depending on a lot of things, some radial systems on earth
are actually far better largely because of water's relatively lower
conductivity. The confusion over the properties of seawater at RF arises
from the fact that refelctions from seawater are far superior to
reflections from any known earth types and this superiority is sometimes
incorrectly transferred to seawater's performance as a ground plane. But
that's for a different time.

Regards,

Chuck

Larry wrote:
chuck wrote in news:hAskf.8744$N45.1460
@newsread1.news.atl.earthlink.net:


Next, you grab your engine with one hand and open the door of your
fridge with the other as you reach for a cold one and you receive an
unhealthy dose of 60 Hz.




Wow...this scenario is pretty absurd, as I suspected, but I'll respond to
these unlikely events, anyways.

Point...there is NO PATH from your neighbor's boat prop to your boat prop
as the water between the boats IS EARTH GROUND....seawater to earth, a
great ground, even if it's a freshwater lake. The path from the
neighbor's absurd boat, taking the least resistance, is from the boat
into the conductive water to EARTH GROUND, back to the AC source. There
is absolutely no path to you and your absurd fridge. Don't believe me,
take ahold of the hot wire on the dock in one hand and simply touch your
finger to the water with the other. After picking up from the deck,
unplug the boat and try it again to see if there's more current...There's
not. You talk as if your neighbor's prop is only connected to your prop,
which just isn't so....

AS to the breaker trip. If you connect AC hot to the engine block in his
boat in seawater, I'd bet 50A would be just EASY! Seawater is a GREAT
conductor. Fresh water is a fair conductor. Try it yourself. Simply
drop the open plug from your boat into the water with the dock breaker
turned on. There'll be a little buzzing underwater before the breaker
overheats....and it eats the guts right out of the plug....