Any Electrical Genius's here?

[Briguy]

I need help figuirng out how long I can leave on a livewell pump before my battery dies. At times I catch bait near the Skyway bridge in Tampa bay the night before fishing. The last time I tried this on my flats boat the battery died overnight and the bait died.(crappy starting battery) I just installed a Sureflo 800gph livewell pump and a 40 gallon tank on my 23 Seacraft. According to sureflo the pump draws 2.75 amps. I have a deep cycle marine battery group 27 with a 130 min reserve. I believe this is calculated at 25amps. How do I figure out how long the livewell will keep running until the battery goes dead?