Should I battery modify or just get a new battery and see what happens?

[Ski]

2004 Launch 21 direct drive.

I got a new battery two years ago and it’s now toast. Should I add a deep cycle as well as the starter battery?

[michael hunter]

If you have a big sound system it would be a good idea. Use a Battery Isolator to keep both charged and draw off the deep cycle to run the sound system.