2001 GSX Starts once, runs, won't start again

[asus401]

I just bought a 2001 GSX with 75 hours on it. The machine is mint. I charged the CT moto-master battery and took it to the lake. Started first try, took it for a 10 minute cruise. Then came back to dock to pick up a buddy and it wouldn't restart. Trailered it home and it started in my driveway...once...wouldn't go a 2nd time. I'm hoping I just need a new battery.
I'm wondering if it might be a 6 volt battery put in on the cheap by the previous owner. No labeling as to the voltage. Or maybe just a dead 12 volt.
Ideas!?

 

[All Things Custom]

when you say it wont start do you mean it will crank over and over but wont start or it wont even crank?

 

[asus401]

It barely turns over. That's why I'm thinking battery. I actually just had the battery tested. Failed two separate tests. Ordered in a new battery for Tuesday. I'll post if she's ready for the season.