Re: wire differences
Yes there is a difference....several in fact. Marine grade wire is specifically designed for marine use. First it is jacketed, (shielded, insulated, coated...) to a higher temp rating than automotive stranded wire. Second, it has more strands in it too make it more flexible and less likely to fail with vibration and rough water. Third it normally has a coated or "tinned" conductor. Each strand is individually coated to help prevent corrosion. In short true marine grade wire is type specific.
My general rule of thumb is that if I am wiring a circuit that is of particular importance, I use marine grade. By importance I mean a circuit that I never want to fail, like engine or navigation. Or if I am wiring a circuit that is in a inaccessible place or carries high current I use marine grade. (Incidentally that describes just about every circuit in a boat.)
A trolling motor circuit? If I had a relatively short run to and from the battery and I could get to it easy.....maybe I would opt for a high quality automotive stranded wire. But I would use 6 gauge, a 50 amp breaker, heat shrink, solder and crimp all the connections. And I would forget the automotive cable and go with marine grade at the last second.

Sorry I am being a bit of a smart @#%.
The truth is if you use good automotive cable it will last a long time in fresh water. (6 gauge though

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