The UV in my part of the world (Eastern Caribbean) is so strong that it destroys many/most plastic items left outside for any length of time. For this reason I store my nav lights, compass, GPS and sounder displays etc inside and only mount them when required. I have used SeaDog 12 volt polarized outlets to supply power as they are well made and unobtrusive when not in use. They come with a flexible pastic cap that keeps out dirt and moisture.
My problem is that the plastic caps disintegrate into a crumbly sticky mess after a year or so despite all being in areas protected by Sunbrella covers. Replacement caps are hard to find and relatively expensive, especially if changing several of them each year or so.
I would appreciate any ideas on alternatives. The cap has an inside diameter of 15/16".
FYI - the SeaDog part numbers are
426142-1 Polarized outlet complete with plug and cap
426143-1 Outlet only
426144-1 Plug only
426149-1 Replacement cap (special order only)
Mike If all else fails, read the instructions If it ain't broke, don't fix it
I looked into the Perko version. I can't tell if the cover is interchangeable with the Seadog. Perko doesn't list the cover as a spare part anyway. Perko uses black plastic which is more UV resistant than white plastic. Unfortunately it looks like the only way to get the cover is to buy the Perko fitting which is horribly expensive. The Perko part number for the complete fitting is 1189DP0CHR. I've got five of them left.