# Starting Current and Cable Gauge

Discussion in 'Outboards' started by CarbonFootprint, Apr 2, 2016.

1. Joined: Nov 2009
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Location: Northern Scotland

Hello,

I'm currently plumbing in a Johnson v4 115hp 2-stroke outboard and need to replace the starter cables.

At present, they're about 9mm/(approx 11/32") diameter including the insulation - the conductors are about 7mm/(approx 9/32") diameter, so I reckon that makes them about AWG 1 and good for about 110A - does this sound likely?

The current cables are so old, the insulation has started breaking down, so they need replacing, but is the same again the best choice? I need quite a run of cable from the starter batteries to the motor, too - about 5m/16'6" once all the wiggles and bends are taken into account. Does anybody know what the typical starting current of this outboard is?

Thanks for any guidance

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3. Joined: Aug 2007
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### CDKretired engineer

The typical starting current is approx. 70 Amps: small starter motors are usually 700 Watts, 10 V arriving at the motor terminals.
5m is very long for starter cables. If there is no alternative I would use a heavy cable from the battery to a junction box near the engine and a lighter one from there to the engine.

4. Joined: Nov 2009
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Location: Northern Scotland

Hello both,

Based on this calculator, I reckon AWG 3 would result in about a 0.5V drop at the starter at 70A, which sounds reasonable to me. I guess the battery voltage drops from 12V when the starter's connected, though - do you know what a typical cranking voltage would be?

Thanks

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