More weird Fish hawk related questions

[chowder]

So when I was digging through the box of weird stuff that came with the boat when I bought it to get out the Moor subtroll monitor and wiring I came across a box in the bottom that had a complete Big Jon Monitroll display, wiring, and fish hawk probe ( apparently it was all Fish hawk   Technology). I’m guessing that the frequency of this 840 era fish hawk must be the same as the X 4 because I have used the new probe with the the 840 in my lil boat. Anybody got any helpful hints on the Big Jon 900 monitor? It’s the same housing as the 840 but the option buttons are very different . Also wondering what would happen if I mounted the 840 era monitor in the back of the boat and attempted to pick up the signal from the x 4 probe on the 840 transducer as well as the x 4  transducer . Then I would have a display in the back of the boat too for free. Seems like it might work?

Edited August 20, 2020 by chowder
Added question