John H. wrote:
I'm keeping the battery from the new boat in the garage so I can put a
charger on it every so often during the winter. The battery is a Nautilus
Gold Marine Deep Cycle, NG-27.

Yesterday I attempted to charge the battery with an automatic charger set
at 2 amps, 12 volt, deep cycle setting. The little green light began
blinking as though all was going well.

About 24 hours later, I noticed the little red light had come on,
indicating I should check the battery. I disconnected everything.

I'm thinking that 2 amps is not enough to charge the battery, and that I
should try it at 10 amps. But, I don't want to damage a brand new, never
used battery!

Ideas anyone?

An inexpensive "trickle" charger can do more damage than good. You
really want to charge the battery with a smart charger, that will turn
itself on and off as needed.