I have a lowrance transducer in the bottom of my boat. I lose the bottom on my HB transom mount at around 10 mph. I know that I can get a y cable and adaptor to connect the lowrance to the HB. My question is will it switch back to the HB sonar when it is back in the water and will it work if I am running chirp on the HB? I tried sharing the transducer with my front unit but found out that I can't as long as I have chirp running. Trying to decide if it is worth buying the cables to connect it or not. Wasn't sure if I had to manually change the transducer in the settings every time that I was going to be on plane.

Also, another question about linked units. When I share one transducer on 2 units and say I set the SI range at 100 on one and 75 on the other or other sonar settings such as sensitivity, Is that only changing the receiving and displaying returns from the transducer or is that changing the signal being sent from the transducer?

No, the Y cable is electrical connections. One leg of the Y cable has the electrical circuit for 2D sonar and the other leg of the Y cable has the electrical circuits for SI and Temp.
There is no possible menu changes to select the 2D sonar crystal in the SI transducer since there is no electrical connection for it.
2D sonar would come from the shoot-thru all the time.

You cannot share CHIRP to a non CHIRP unit.

When networked, you can control the 2D sonar separately, but if you adjust the SI Range with either unit, it changes both units.

The unit that does not have a transducer connected should have Sonar OFF.

thx Wayne