Not quite sure about this one, as the tanks should fill each other, Alot of times when fishing alone and gassing up in the AM I will fill the left saddle tank full, and over the course of the day it will siphon into the right tank. As for the gauges, i wish they would just do away with fuel gauges as they are extremely inaccurate, and this has been on every boat i have owned. Even my brand new p4 at the time has not had the gauges working correctly (and still dont) since i got her. But i would rather just lift a hatch and look for myself then trusting the gauge. Sorry I cant help with you problem as to why the tank is not using its fuel but BCB and others will be along shortly.Jay Law