I have a (new to me boat), it has a 2010, and a 3210 MFD's connected to a GMS 10. I was given a 4208 with a GSD 22. I would like to be able to connect these units into a NMEA network but can not fine the best way to do this. I do not know the type of transducer that is on the boat, other than it is a through hull.