Operate fish finder without transducer?

One more quick question while you're here: my manual indicates that the unit has a NMEA output, but the description sounds like it's an input.  I have a vhf with GPS.  Can the elite 5x take GPS input?  If so, is it RS232 level or what?
Thanks

No.  It send output your depth info to other items on a NMEA0183 network (old school).  Ignore it all together.

Once you go NMEA 2000 & Ethernet ... you won't want to ever deal with 0183 again but that's a WHOLE NOTHER' thread all together!