I think it worked - I need to try it on the lake.
Long story short the MercMonitor has troll control of .1 mph built in, PROVIDED you can get the SOG (Speed over Ground) into it from you GPS via the NEMA 0183, or 2k.
IF NOT (no speed over ground) your can still do troll control via RPM (10 rpm increments) control.
SO ... I found a. Link to wire them directly (Humming bird won’t send it over the coaX nema but it will receive engine information to the humming bird)
The link shows how to connect the wires (Nema 0183 ground, and tx to rx between the SOLIX and MercMonitor, and then adjust the Baud rate in the Solix in order to get them to talk.
I followed the instructions - and my MercMonitor now gives me the SOG troll control Option ~. YEHAA !
I have to test it in the next couple of weeks.
Here is the link http://www.bbcboards.net/showthread.php?t=858784