Help Me Please Gauge Not Working???

[Ktrain]

Here is my deal, I have twin 1998 mercury 250 efi's on my boat. They have a multifunction gauge that showes overheating, water in fuel and oil warning. Now here is my problem, my portside gauge does not work and when i turn the key i know it should beep and then the gauge should light up. well it dosen't light up and the "beep" is very, very low compared to the other motor. i got under there today and everthing "seems" to be hooked up correctly, changed the light blubs and still does not work...........I NEED HELP WHAT SHOULD I CHECK NEXT..........???

thanks in advance

[The Big Al]

Ground wires. Anything grounded, check everyone you see.
If it has any corrosion clean it.