CJ
There is an Ethernet hub. But before you spend the money double check with Humminbird. I did not view the above attachment regarding compatibility.
I have a 898 and 788 with the Minnkota Terrova I pilot all networked so they talk to each other through the hub. Think of the hub as a connection point where all the cables come together an allow all the graphs and trolling motor to speak to each other and share information. I can share way points btw graphs, all can view from one transducer or individual transducer. There is also a separate networking cable for the 788 that you will need.
If you decided to pick up the hub. I would suggest wiring a switch to it so that you can disconnect power when not in use. It will put a light drain on the battery.
I would contact Humminbird customer service. They are fantastic. When I bought my stuff they were very helpful and I had no surprises when connecting everything together. And Im not the most handy guy when it comes to this stuff.
Your situation is a little different in that you are connecting different generations of electronics together. So please double check with Humminbird before you spend your money.
Below are links to the hub and the thernet cable adapter you will need.
https://www.humminbird.com/Products/AS-ETH-5PXG/
https://www.humminbird.com/Products/AS-EC-QDE/
Again I think it may work but please double check with Humminbird tech support
Bob