12v battery questions...

Bought a boat that hasn't been used in over a year...

I'm assuming if a cranking battery shows 3.6 v its gone bad? Put it on the charger and there's no progress.

Also, I have another trolling motor battery I'm trying to check on. It has been on the charger since around 9 am and it does show a small amount of progress and when I unplug the charger it shows to have around 12.6v. What do y'all think?

I would replace the cranking battery without thinking twice about it. It sounds like they are all bad based on your results. When batteries stay discharged for long periods of time they will never be the same again.

I was really hoping that at least one would be ok... Wishful thinking I guess. After just buying a boat I want to cut out as many expenses as possible.

I have three blue top optimas I'll sell you for $25 ea. Still hold a good charge and been using them, I have two group 27 I used for trolling and a smaller cranking. Are several years old but can't take a chance with a bay boat that far from shore.....just replaced all 4 the other day and one grp 27 gone bad three still good Might get you a year on the cheap. Shoot a pm if interested I'm in Emory.

A 12 volt battery reading 11 volts is dead....one reading that low is trash.

unfortunately....buying a new boat is expensive...buying a used boat is more expensive. Set aside a fixed amount every month for boat repairs and you'll be fine. I speak from experience. I have 3x more money invested in maintaining and upgrading my boat than it's worth on NADA.

If you don't replace those batteries, you won't be thinking that it was all that great saving money when those batteries shut down a fishing trip.

It's best to just replace them all and have the peace of mind that they're good for a few years. Plus by starting fresh, you can maintain them properly from the get-go (keep water in them, and charge them up right after being used).