Capt. Lenny

I have 3 Lowrance HDS Live units on my boat and all are connected through a NMEA 2000 backbone. My Yamaha engine and the gauges on the dash are also connected to that backbone. When everything is on and the engine is running I can't get engine data on any of the Lowrance screens. I don't even get the little engine icon ao the left sidebar of the screen. What am I doing wrong or what do I have to do?