I am not sure if it is buring diffrent or if the gauges are off.

I put $200 in each tank this weekend. By the end of the weekend one tank used about 1/4 and the other went from 1/2 to empty.

The motors are carb 454's. Is it even possible for one to use more than double what the other engine used. I could understand if it was a little off but its way off.

Anybody know of a good way to check how much fuel is in each tank or find the sending unit for the gauge?

If one engine used that much more fuel than the other it sure would seem you would notice some performance/ drivability issues with one of the engines.Short of putting fuel flow meters on the boat you could top off both tanks till they almost puke fuel out of the vents and go run the boat for a while and see how much each tank takes to fill up completely again.

Had this happen on a cabin cruiser, your rpm gauge can be off thus you think the motors are in sinc, but one is really working harder than the other. It took us a week to figure it out.

WILL

Unless you fill them both full and then run them for 5 hours or more, you won't really know if its a usage issue or a guage/sender issue. You then need to refill them full and see the difference. There are 2 adjustments on the senders and they are very sensative to adjustment.

One of my engines uses about 2-4 gallons more for a fill up, but thats it.

Check the fuel return lines. Ain't the first time Ive seen the returns from both engines end up going back to the same tank

He has carb engines. No return lines.