“Hi Nickas, There are valves in the center aft bilge that will allow you to select from which tank you are drawing fuel. They are marked MAIN and AUX. The AUX tank is the 50 gallon one. If you run that tank dry you can get air in the fuel system, so it’s best to manage your fuel and not let either tank run dry. Call me at the office if you want to discuss. Regards, Joe Brenna V.P. Customer Service, 727-548-1260 ext. 229”