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