Check to make sure your gain settings are proper. Which head unit do you have? Depending on the year we might have different gain settings to recommend.
Newer boats with the MB Quart head have the gain knobs with their indicators pointing at the first hash mark up from all the way down. That is the current recommended gain setting at the plant. Make sure the bass boost setting on the amp is totally off, and that the hi-pass crossovers are engaged. Run through your head unit presets to make sure that the loudness control is off.
You probably do not have two sets of RCA cables, but only a single RCA pair from the head unit to the amp, so it is likely a gain that is too high.... Turn the gain down that looks higher than the other and the crackling will likely go away.
Adding a larger amp can help, but there is no reason for the stock system to be acting funny.... Check the settings, and then post back and let us know-
Last edited by philwsailz; 04-26-2010 at 10:44 AM.