King-- I don't know about your particular epoxy blend, but epoxy used for boats needs to be covered by a UV-inhibiting finish. It can be a clear finish, but it must be there. I'm guessing the goo you're using is the same.

I've been tinkering with rebuilding a small boat a little bit at a time, and I've noticed that sunlight is no friend to epoxy. I'm starting to get some peeling and flaking of unfinished epoxy coatings. Of course, the boat sits in the weather and in full sun, so it would show there quicker than on oars that are stored. This phenomenon isn't something that just I have seen; it's common enough that there are warnings about it on wooden boat building sites.

Keith