Join Date: Oct 2008
Location: South Coast Ontario
Thanked 90 Times in 80 Posts
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I think you already know the answer.
However... as a failsafe, try a different charger. The problem may be the charger, not the batteries.
Having said that, assuming your demand power draw is give/take 0 (nobody on the boat, so no systems running other than stereo memory and maybe a bilge pump?) I am surprised your batteries are flat.