To prevent sulfication the batteries must continuously brought back up to near 100%. The last stretch takes hours, so solar is a good supplement.
My Outback Nano-Carbon better tolerate a Partial-State-Of-Charge. They are no longer on the market.
I heard better things about Firefly Oasis carbon foam LA batteries. They don't need to be brought up to 100%, saving boaters a lot of diesel. Lasting X3 longer. But at these prices you might as well go Battle Born lithium.
https://www.emarineinc.com/Firefly-O...oup-31-Battery
If your do go for 6v flooded cells, consider a watering system.
https://watermybattery.com/?gclid=EA...SAAEgLPN_D_BwE