Does cured crystal clear epoxy resin need a finish coat over it?

For the most part the answer is yes, but some crystal clear epoxy resin systems provide a little more UV resistance than others. For example, West System 105 Epoxy Resin combined with West System 207 Special Clear Hardener has an ultraviolet-inhibiting additive that, when cured, improves UV resistance. However, it should not be relied on to provide effective UV protection. For that, you need to apply a UV-filtering varnish or urethane clear coat over the cured epoxy. TotalBoat 5:1 Traditional Epoxy Resin combined with TotalBoat Crystal Clear Hardener does not provide UV protection when cured. It also needs a UV-blocking varnish or urethane clear coat applied over it.