Battery cable- what gauge?

[gradyrod]

I am adding a Second battery to my Fisherman 204. I need to make up a battery cable to go from one side of the boat to the other where I will have a 1-2-Both switch. Length of cable run is about 9 ft . I have a 175 Johnson and I was wondering what size Batt cable to use from the new starting battery over to the switch. Would 4 gauge do it?
Thanks.

Rod
1985 Fisherman 204

 

[BobP]

Battery cables are usually No. 4 or heavier No. 2 awg.

I would tend to go with No. 2 myself even though the No. 4 will get the job done.

My concern is not ampacity, it's voltage drop.

If at the time you need to start the motor and the battery happens to be run down, the more voltage to the motor may make the difference between hearing just a click or a crank and firing - to head home.

But that's just me.

My boat had all No. 4 as new, I changed to all No. 2. when I redid the battery switches.

 

[Grog]

Go #2, it's basically a 20' run for the power (you have to count to and from the battery for the length).