Thanks Greg,
I think I've just worked out the problem, yes this is quite new, only found it this afternoon whilst trying to solve the Spot Lock point problem.
I did the firmware upgrade to 7.120 outside the boat so yes, no sonar tab as there was no transducer connected to each unit.
I just put the sounders back in the boat as they are linked by an Ethernet switch with the iPilot Link Minnkota.
The sounders "found" each other over Ethernet successfully. The bow unit is the one I was having trouble with.
It found the GPS receiver in the Helm unit and synched to it quite successfully. I now have all of the menu options back.
Unfortunately neither sounder lists the Bow units internal GPS as a source option.
Looks like I may have a Bow sounder with a dead internal GPS.
Could be worse, it could be out of warranty!
Thanks,
Geoff
PS, I'll fill in the Spot Lock point resolution in my other thread so as not to cause confusion between two unrelated issues.