multiple issues

i had a helix 10 g4n mdi on the bow with a mega 360 on an ultrex , using a y cable to have 2d and 360 at the same time,
it worked great , I put a 10 g4n msi on the console. never got to put it in the water but looked normal for one running
out if water, Then I added a 5 port and networked the 2 units , put a shoot thru the hull in with a y cable, never tried it in the garage , i tried to get the dash unit to recognize the thru hull but when you try to select it it would blink back and forth really fast and it would change to the map page on it's own , the only 2 d it would show is the one from the trolling motor transducer . I am not sure what to do.

When you add a shoot-thru transducer with a Side Imaging transducer via Y cable, the 2D piezo in the SI transducer is disconnected (no wires). The shoot-thru is connected in its place (wires). Nothing is changed except the physical location of the 2D source so no menu changes are needed. If you are lost for the correct setting, do Restore Defaults and the console unit will be returned to the factory setting that matches what you have connected.
A Helix does not recognize any transducer except a MEGA 360 (it has a XID circuit that changes all the Connected Transducer choices to ones involving the MEGA 360).