Couple of more things to try if the previous suggestions don't help. With the crackling speaker removed, get about 15 or so feet of 14 gauge two lead wire and run it from the output channel of the amplifier which goes to that speaker (right or left) and see if the speaker still crackles. If so, then try pulling the other bow speaker out and hook it up to the original wires on the crackling speaker side. If it still crackles, then the problem is either the amplifier or something coming to the input side of the amp.
At that point, I'd be considering warranty work, because the problem is either the head unit (unlikely because apparently the other speakers on the same side of the boat aren't crackling), wiring on the input side, or the amp itself. These Wet Sounds systems use DSP amps with no ability to adjust or test the input side, unless you cut into the wiring on the input side which goes to the plug in the amp. You don't want to be doing that. If you go to the dealer under warranty, they can switch parts out (like the input harness, amplifier, etc.) until they find the problem.
Chances are it's a loose connection on the output side at the speaker, as noted above. Or a bad speaker, or the wire itself going to that speaker is broken or compromised inside the insulation. One of the suggestions you've received in this thread will isolate it.
Please let us know what you find.
Jeff