If I relocate the battery (s) to the port settee locker of my 26.5 to help offset the weight of the outboard, would a #2 awg cable be large enough to carry the current back to the motor? Let's say about 20 ft. Or, how many amps are required to spin that 9.9 Nissan two stroke?
Amps
- Thread starter Bruce Rowe
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You can use the calculator at the bottom of this link: http://www.powerstream.com/Wire_Size.htm . It assumes that you know how many amps your starter requires. Will there be any other loads on the battery or is this a dedicated start battery?
Well, that's the rub-I really don't know what it takes to spin the motor. I will probably go with two batteries just for safety, although replacing incandescent bulbs with led's might make the point moot.
Playing with the numbers
I too, do not know how much current the starter motor draws but playing with the calculator Ed provided yields 56 amps on a 20' one way limit. That is based on the %voltage drop of 3%.
I know my 50 HP diesel has a 1.2 kw starter which would indicate that it will draw around 100 amps when turning. Stalled is another mater however but since the key prevents the circuit from staying on without my holding it an I would surly note the engine not turning that is probably not a big concern (unless the contacts jam)
I can't believe a low compression 10 HP engine would draw anywhere near even 50 amps.
If you have a manual it will probably list the specs for the starter motor as xxx kilowatts. Just divide that by 12 volts to get the operating amps then add a 10% safety margin for slow cranking and surge currents.... basic engineering. The starter might even have a data plate on it with the same info. In a pinch you can look at the wire that goes to the starter inside the engine and get an "absolute maximum" current flow and calculate backward from that.
I too, do not know how much current the starter motor draws but playing with the calculator Ed provided yields 56 amps on a 20' one way limit. That is based on the %voltage drop of 3%.
I know my 50 HP diesel has a 1.2 kw starter which would indicate that it will draw around 100 amps when turning. Stalled is another mater however but since the key prevents the circuit from staying on without my holding it an I would surly note the engine not turning that is probably not a big concern (unless the contacts jam)
I can't believe a low compression 10 HP engine would draw anywhere near even 50 amps.
If you have a manual it will probably list the specs for the starter motor as xxx kilowatts. Just divide that by 12 volts to get the operating amps then add a 10% safety margin for slow cranking and surge currents.... basic engineering. The starter might even have a data plate on it with the same info. In a pinch you can look at the wire that goes to the starter inside the engine and get an "absolute maximum" current flow and calculate backward from that.
I have a 9.9 Honda 4 stroke on my boat. It draws about 50 amps to start, I use a 70 amp circuit breaker beside the battery and it works well. The breaker/fuse should be sized for the wire size you use.
Bob
Bob
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