"Capt John" wrote

The #4 sounds like over kill, and you wire run is not back and forth,
it's from point A to point B. My old boat was 27 feet, my power winch
called for #6, much cheaper than #4. It worked perfect, that winch is
being used occasionally, not constantly. If it were being used for
extended periods of time the larger wire would be justified.

I beg to differ. When calculating wire size from amperage it is ALWAYS the
total run out and back to the source to get the total resistance.

A 600 watt windlass is going to draw 50 amps at full rated load. #4 wire
has a resistance of .000253 ohms/foot so 72' will have a resistance of
about .01822 ohms. By Ohms law A*R=V so 50*.01822 = .93 volt. or about 8%
loss. About the most you want to loose.

#6 has a resistance of .000403ohms/foot or .029 ohms over 72' which will
drop the voltage by about 1.5 volts. Net result is you don't get all the
power that the winch needs and the motor will overheat and possibly burn out
a winding.

The only way to use smaller wire is to use less of it. Cut the run to 30'
out and back and you can use #6. Best thing to do is mount the solenoid
right by the windlass and run the wire directly from the battery to the
solenoid. Then put the control switch where ever you want. The control
lines don't carry much current.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com