Motor wires to battery?

[nedyarb2000]

I bought a used 20' ft blazer last year. Last night I replaced the sump pump. When rewiring the battery I noticed the main motor cable had three cables one red, and two black. I hooked the thicker black and red too the neg and pos terminals. But where does the smaller black one go? Thanks Rob

[briscoec]

You should have a single 10 ga wire with an inline fuse from your positive battery terminal that splices to that extra wire. That is the "hot all the time" lead that allows your bilge pump to turn itself on if it sees water...... Otherwise you would not know to turn it on until the back of the boat is low in the water.