I have a similar boat, Prov 1775 with a 24v Terrova. I went from Group 27 to 31's and I can get maybe 5 hours if I'm trolling exclusively with the batteries and keep it around 6.5 or less. You gotta troll with the wind though to keep the current draw low.

I have 90HP 4 stroke, which will troll about 1.9 - 2, so what I do from this time of the year on, is use the gas motor to propel the boat and leave the Terrova at 4 and use it to steer. Batteries will last at least a full day, maybe more doing that. I may upgrade to Lithiums in a couple years when I need new batteries but they are pricey.