[sluggo]

I am experiencing the same issue on my 2005 Sovran 3600.  The head unit does derive power from the sub woofer through a 15 pin D sub cable running between them both.  I have had the head unit out it isn't the easiest but it does come out.  The power to the sub on my boat comes from a power conditioner (why? I don't know) below and behind the fridge.  I am working through this problem right now.  In my case the AC outlet breaker trips.  The power cord for my sub woofer routes behind the cabinets.  I am waiting on a replacement power cord to come in and plug it into a different location to bypass the power conditioner and isolate the problem prior to ripping a bunch of stuff out unnecessarily.

well I swapped out the sub woofer, found a reconditioned one on line, the price was too bad, but the shipping!!  I had to negotiate that!  After I swapped that out, everything worked just fin.  On youtube there is a video of a repair for the sub woofer, and many times its the fuse!!  so right now, I am having the that replaced, and I will see what I get.  If you make progress, let us know!! TIA