1978 Carver santa cruise problem with shift box

[Flippenout]

1978 25.5 ftCarver Santa cruise cabin cruiser. Duel helm set up both mechanical lines are working. The part where you shift it from top or to bottom is not working correctly and at the same time connects both helms for steering to the stern drive(Btw is a volvo penta?) It has 3 square tubes in a aluminium box that top rail for top helm middle goes to stern mechanical line, bottom of square rail is for cabin steering. Middle square tub has shifter engages top and bottom helm. I don't know exact name for it or terminalogy, whats the name , maybe systematic it is why I'm here?
but with your , with the name I can get a break down of it and then I can fix it? hopefully ,maybe I can finalie go fishing

[Viper]

Clint, is this boat new to you? Has this issue always been there since you got the boat?

I assume the engine has been running while you've tried to shift gears?

[Flippenout]

[attachment=0]IMG_20210407_034759978_HDR.jpg[/attachment. this is new to me. Last time we took the boat out . Neither helm worked. Because the boat sat for 5 years and mechanical steering line froze up with corrison,so steering did not work. I replaced the line and now, will call it "junction box" for the two helms is not working correctly to the stern. I posted a picture.

Let me do a little more detail. So this was my dad's boat and he loved to fish. He passed away and the boat sat on my mom property for 5 years. It wasn't properly been taken care for. So I rebuilt the motor, replaced the heat risers, bought new battery's fixed the stern drive, replaced the mechanical steering line from the top helm. Now this is the current problem and almost to a stand still. I believeni can fix this issue but if I can't might need to get a professional that works on marine.