Wire size

Keepi time

Petty Officer 2nd Class
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Jun 12, 2011
Messages
103
I am trying to figure the correct wire size to go from my battery to my engine. My current set up is a 17ft cc with the battery under the console with my wire going to a terminal block mounted at the back of the boat. I am wanting to do away with the terminal block and redo the wire straight from the battery to the engine. It's about a 12ft run. Question is what size wire should I use. 4 awg or 2 awg. Thanks for the replies!
 

Don S

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Aug 31, 2004
Messages
62,321
Re: Wire size

What engine? I know it will take smaller cables to start a 9.9 hp outboard compared to an 8.1L MPI Big block V8 IO.
 

Don S

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62,321
Re: Wire size

Personally, I have no clue what the specs are for a 90 Johnson. so can't answer accurately.
 

gm280

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Jun 26, 2011
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Re: Wire size

I am trying to figure the correct wire size to go from my battery to my engine. My current set up is a 17ft cc with the battery under the console with my wire going to a terminal block mounted at the back of the boat. I am wanting to do away with the terminal block and redo the wire straight from the battery to the engine. It's about a 12ft run. Question is what size wire should I use. 4 awg or 2 awg. Thanks for the replies!

Once you know what your starter draws, then you can used this chart to figure out the correct wire size for the distance you will run the wires...

wiringdiagram.jpg

Bear in mind that these sizes are for full time running for stated current. Not telling you to use a smaller size or gauge, but I am telling you that you will only be using the starter’s full current draw only while starting your engine. And the easier your engine is to turn over the less current it will take also. So you could conceivably get away with a little smaller size for a limited amount of time...
 

Keepi time

Petty Officer 2nd Class
Joined
Jun 12, 2011
Messages
103
Re: Wire size

Thanks GM 280, exactly what I needed! I think #4 will work. I remeasured and I'm looking at about 10 ft. Thanks again!
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: Wire size

Thanks GM 280, exactly what I needed! I think #4 will work. I remeasured and I'm looking at about 10 ft. Thanks again!
You need to use the round trip length.

Better off to use a calculator where you enter the %drop you can tolerate rather than the chart posted which you have no idea what the % drop it represents.
DC Cable Sizing Tool - Wire Size Calculator - MM2 & AWG - solar-wind.co.uk

Or use this calc and size wire to get between 10 and 15% voltage drop
http://videos.cctvcamerapros.com/voltage-drop-calculator
 
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