Fuel Management gauge to GPS

[hookemup29]

Hello, anyone ever had difficulty getting the FM gauge to communicate with the GPS from a Lowrance LCX-27 unit? Id like to get the speed readings from the GPS so I can get "miles per gallon" readings. I cut off the end on the plug from the FM gauge and connected the white wire to the data out wire on Lowrance harnass with no luck. I set the dip switch to GPS also. What am I doing wrong.... can anyone offer any help? Thanks in advance!

[boats.net]

That should be it, check that it is correct wire from Lowrance.
FMM GPS Connection.JPG
FMSettings.JPG