I am 74 and have a helix 8 g3n up front and a 2 g2n at console How do I pair them? Also, I and going to get another just for mapping what do I need to be able to view all three on my 12 unit?
Helix models starting in the second generation that have n in the generation name are Networkable. That was done since Helix 7's are available as non-networkable or networkable.
You share data via Ethernet network.
Each Helix display needs the AS EC QDE Ethernet Adapter to connect an Ethernet cable to it == it's because of the quick disconnect cable feature.
An Ethernet cable has two ends so that is two devices that can be connected together with a single cable.
To have more than two devices networked requires an Ethernet Switch (hub) AS ETH 5PXG. Then each device would connect to the Ethernet Switch.
Helix units do not share any mapping of any kind with any connection, they will share waypoints, sonar, and Ethernet devices.
If you want the same mapping on all units, each unit would need a matching map card.
Second and third generation Helix units have different 2D sonar standard frequencies.
Also there is more to discussing sonar units, it's the exact model they are which will determine what they can share.
There is the CHIRP model which is 2D sonar and GPS.
There is the DI model which is 2D sonar, Down Imaging, and GPS
There is the SI model which is 2D sonar, Down Imaging, Side Imaging, and GPS.
All three of those models can be a GPS/Map unit without a transducer connected. The CHIRP model would be the lowest cost and a CHO (Control Head Only) model would be even a lower cost.