Have everything mounted for Livescope with Garmin 93svUHD chartplotter.

GLS10 Livescope Blackbox mounted in compartment in stern = check
Power to GLS10 Livescope from cranking battery = check
Transducer mounted on Pole = check
Chartplotter mounted on bow = check

For some reason and I may have dreamed it.....I was thinking I was told that the data cable from the GLS10 box would also serve to power up the chartplotter as well. That it was both the power and data cable to the graph and I may be completely nuts

If that is not the case, which battery should graph be ran too. I have blue top Optimas 1 for the start battery (the one the GLS10 is hooked too) and two for the trolling motor up front. Its a 12volt Minn Kota but the two batteries are run in parallel.

If I run to the back of the boat what size wire should I use?

Thank you all for letting me ramble with this and thanks for the help you have provided up to this point.