I second the fire hose idea. I know from experience that Sunbrella has poor abrasion resistance. I bought a set of fender covers and they don't last.
I use fire hose on my aft rail for sun protection and also ding protection while fishing. The stuff holds up well and the inner rubberized lining keeps it in place. I suspect a well-fitting segment on the power line would retain flexibility and be well protected, but might be a bit heavy and clumsy if coiled.