I think it might be possible to do an Ethernet to Bluetooth adapter on both ends ...... Or maybe even a wifi to ethernet on both ends....If someone wanted to do some experimenting.
As long as no transducer is attached....and small dedicated battery was used for power.....You could put the unit anywhere in the boat you want.

I was wondering if the Onix ci model and a transducer attached to a sm 2000 module ...and maybe a 360...would be able to be used this way. Only problem with Bluetooth is that I don't think it is very fast......Might have to do an onboard wifi network to accomplish it.