OK, dumb question.  I've tried to charge a 12v battery and my charger keeps reading "fault" and won't charge the battery.  I didn't buy the battery.  It came with the used boat I bought.  It looks like a wal-mart cheapie.  I pulled the battery out and grounded the negative terminal and it still won't charge.  Is this a non-rechargeable battery?  What is the difference between a chargeable and a non-rechargeable battery?

No, it's not a non rechargeable battery.   It's a junk battery.   When you go to Wal-mart to buy a replacement, buy new ones for the cranking battery and TM battery.   Will make you a much happier fisherman when you don't have to worry about batteries.  Not too sure what you mean by "Grounding" the negative terminal but that does nothing.

The battery is either bad or so far discharged that it won't respond to the charger.  I have had batteries that would only accept initial charge from a two amp charger.  If you have a hydrometer, you can check the cells.  When you buy a replacement, I recommend that you get one with lots of reserve, not cranking, amps.  You may not be able to get it at a place like Wally World.

Any battery that is at a discharge level that will not let the charger come on, is going to be junk.  It will never take a full charge and will give very lilttle run time,  If it's a cranking battery, it will only fry the charging system.

Those big, yellow group 27's Wally world sells will give you as much run time as any of the cheaper batteries, and even some of the not so cheap batteries.