It's very simple to add. Just order it. You attach it to your TM or transom, whichever you choose, then run the lead back to the unit and there is another terminal bay to plug it into. That's it. When you turn the unit on again, it auto runs a diagnostic and adds the temp sensor. It will beign working. Good luck. I bought a $15 MARINE temp sensor at Wal-Mart and glued the sensor to the bottom of my TM, then ran the wire, mounted the LCD next to my graph on the bow, (all took about an hour) and when it got WET from the rain, it died. A MARINE TEMP GAUGE for cryin out loud. Anyway, have fun.
Have mine attached to the transducer out the back of the boat. I think i'd really like to add one to my Eagle up front so while i'm trolling I can see the temp as well (don't think I can split the temp feed from a humminbird to an eagle). Easy and runs great!
Rick - I do not know anything about these electronics, didn't mean to imply that you could do it with a humminbird - don't know?
Only thing I could think of would be to somehow get another head unit end plug with some cable and splice it in, don't know if it will work - i've read on the BFHP a discussion on trolling motor transducer where folks said you could and you couldn't do it.
Anyone else know if you can splice temp gauge wires??