ozzie-crawl,
I think the carbon fiber thingy isn't causing the interference. There are just too many other possibilities for potential interference to even worry about the CF thingy. Just keep in mind that carbon fiber is a conductor (the amount of conductance varies greatly, depending on how that fiber was made), so, treat it as you would metal in an electrical environment, sort of.
You might make sure that your boat's antenna isn't 'shielded' by the CF, that could make some difference. It would also be a fairly good idea to snoop around and see if you could find any other potential 'interference' causing things in your boat.
Wish it were simple, but it isn't...
- 'Doc