Wire size is a function of amp load and distance. The #10 leads on the
windlass are only about 2' long so they can carry 50 amps with a voltage
drop of only 2%.

With 50 amps on a 72' run #4 is the absolute minimum size you should use.
Even then including the windlass leads you will be close to 10% voltage
drop. Using #8 you would loose more than 20%.

How are you routing the wire to use up 72' on a 27' boat?

--
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

"Don Mahony" wrote in message
...
I am installing a Lewmar Horizon 600/900 horizontal windlass on a 27
foot power boat. The users manual says to use #4 AWG marine grade wire
from the battery to the solenoid to the breaker to the windlass and
back to the battery. The wire leads on the windlass are #10 AWG.

I know the concern here is with voltage drop to the motor but the cost
of the #4 wire is huge. Rather than following the general guidlines in
the manual does anyone have a better way of calculating exactly what
gauge wire would be needed for this installation?

The total run from the battery to the windlass and return is 72 feet.

Don