You will get a LOT of varying opinions on what type of wire to use.
I used this stuff from my cranking battery to a dedicated fuse block at the console. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I used the 12 gauge version of the same wire from the fuse block to the bow unit.
The reason I used this wire was because it has a VERY tough sheath, it is tinned stranded and twisted wire. The twisting in the wire helps make the wire less susceptible to interference. I have virtually no interference with my current setup which includes a 24V Terrova trolling motor and have not had to add any chokes to the wiring. I also used a hydraulic crimper with marine grade terminal hardware.
The only drawback I have found with this wire is that stripping it is a little difficult.