96 Yamaha Fuel Management Question

I just recently purchased a boat with twin yamaha 150 saltwater series engines. Had to change the fuel management gauge. Bought a used gauge from a friend of mine. Everything works fine, but the readings I am getting seem very low. For instance at 4400 rpm's it is saying I am burning 3.5 gallons per hour total. I would love to believe this is correct, but I am sure it isn't. Does anyone have any idea how to sychronize, or set the switches on the back of the gauge? I bought a repair manual, but it doesn't really go into specifics about the fuel management gauge and I do not have the manual on the gauges. Also, everytime I stop the motors, the gallons used resets itself to 0.0. Any help would help, I want to know how many gallons I am burning as to make sure when I divy up the gas amount I am not losing.

[boats.net]

I emailed you some information on fuel management.

Thanks

Thanks so much. I will calibrate the gauge first thing in the morning.