Have a new opti blue top that is dead and won't charge. I left the power switch on after the last trip. Will most battery's not charge after being fully drained?

Also about to hit walmart for a new cranking battery. Any suggestions

Sometimes they get so low that trickle chargers or maintainers can't charges them. You can move it to start and jumpstart the motor with it connected and let it idle for a bit(Didi this with mine once) or borrow a hot charger somewhere.

This. ^

Great I'll try that
Thanks

I always keep a manual charger in my arsenal just for that reason. Good luck.

You need a battery charger that charges AGM batteries! If you discharge an AGM battery, a regular setting or battery charger will not work!

I use one of these
https://www.basspro.com/shop/en/schumacher-automatic-speedcharge-ship-n-shore-12v-battery-charger
for my cranking battery, truck, lawn mower, wife's car...
Has settings for standard, AGM or gel batteries

As a maintenance note, I suggest a solar charger for the boat when it is sitting... Just hook it to the battery and put the panel where it can get sun... they are not too pricey and it works well.

whats a "hot charger" i have the exact thing going on right now....same blue top and it has zero volts.

I'm having battery issues with my yr. old series 34 agm interstate cranking battery going dead after 3-4 hrs on the water, just spoke with a dual pro ( chargers tech) and he told me that the charger I have ( quad 4) will charge a agm battery to full charge, so it's back to the interstate store for me

I had a complete set of (3) Optima Blue Tops a few years ago. They charge faster and hold a charge a little longer but I learned they do not last any longer than cheap Walmart batteries. Once they started dying off I had them tested which showed they were still good but would not take or hold a full charge. Put them on a charger at my companies shop which would apply a much hotter charge but they still wouldn't hold it. I replaced them all with Everstarts from Wally World. Just replaced one of them which was 4 years old. The other 2 are still going strong. I have a Noco Gen 3 30 AMP charger that I would also recommend to anyone.

Just put a regular charger on it for an hour or two and the onboard will pick it up. We keep a small charger just for that.

More times than not, a fully drained AGM will not charge back up.

If you hook it to another battery and hook the charger up you can trick the charger into thinking the battery can be charged. Some chargers have to see some charge to charge. Worth a shot before you buy a new battery