1999 OX 66 fuel flow Sensors

My Fuel Management Gauge is only showing one engines fuel flow and not indicating which engine it is reading. I need to isolate if it is the Fuel Management Guage or the Fuel flow Sensors. The Guage shows all indicators when power is turned on but I cannot use the control buttons to show Port, Starboard independently.

I have twin 1999 OX 66 250HP yamaha's. Questions I need help on:
1. How can I test the current flow sensors for operation? Can I use a Volt Ohm meter to test if they are sending out the proper signal?
2. How do I test the Fuel Managment Guage
3. What is the part number Fuel flow Sensors and the Fuel Management Guage?
4. Where can I buy them on line?

Thanks

Hcheli

[boats.net]

Remove the sensor and use compressed air, blow through sensor in direction of fuel flow to see if get a reading on gauge.
See number 15 in diagram
Yamaha Outboard Parts 2005 2005 OUTBOARD RIGGING GUIDE INSTRUMENTS DIGITAL Diagram

[jb123]

i also always have intermittent issues with my FMG and sensors. check your electrical connections at sensors .