Mornin'...

My son got advice from another that running a larger power supply wire to our Helix will improve image quality? Like 10ga or 8ga. It's not finding a place in my brain where it makes sense.

How long is the unit from the battery?

On my 18 footer, I ran a 6 gauge to a fuse block at console, used to power 3 units. The 2 units in front have 10 gauge from console fuse box to bow units.

So the length of wire from power source will determine wire size.

About 10' of wire from the battery to the fuse block. Only running the one Helix 7. If I wind up at ABC auto I'll grab some 10ga 2 conductor to run to the fuse block. It's about time for the boat to come home from the slip for the 100hr service so we're working up our 'wish list'.

Order some good marine wire. Not sure how long regular auto wire will last, but should be fine for a few years.

8g power and ground from the battery to the console. In the console, mount a BlueSea 6-way fused distribution block with 6 grounds on it too. Run dedicated 12 or 10 gauge feeds to each graph. It will be more than sufficient for 4 graphs, and a sonar module or two. The trick is to prevent severe voltage drop. As for picture quality? I guess it depends on the equipment. My Lowrance graphs and AT2 look great with 12.6 volts or higher.

We make both 8ga and 10ga wire kits, with simply a couple graphs, the 10ga kit will be more than enough for you.
Look at it as water will on flow as much as your smallest hole and the distance restricts it. You want to increase the size of the wire for greater the distance.

https://www.bassboatwired.com/products/bbw-graph-power-harness-kits