Extra Battery
Your gonna want a second battery just to be safe. If your like me you'll put the stereo, then speakers, then more speakers, then you need an amp, and so on and so forth. I'm sure that the one battery could get you by, but you don't want to be stuck on the lake or in a cove with a dead battery. It's just safer. You should check out the threads in the seadoo boat modify section, there is some good info and quite a few posts on installing stereos.
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