I have 4 Trojan batteries in my boat and they have been in the boat for at least 3 years as the boat has been out of the water that long. How do I know if they are any good and should I pull them out before winterweather comes?
Fully charge then then do a capacity test ( look it up). I never took mine off the boat during the winters in Boston . Just fully charge them, check the water level, then completely disconnect them
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Don't ask a bunch of unknown forum people if it is OK to do something on YOUR boat. It is your boat, do what you want!