Thank you all for the hints/tips. I'm picking up some 3/8" flared copper washers from Grainger later today. Before using one I will try and work (tighten/loosen/tighten/loosen) the fittings one more time before going the washer route. I've already lubed it and even used a magnifying glass to inspect for cracks or nicks in the mating surfaces.
This is a boat engine I'm working on so I need to be 110% sure there are no leaks.
Kurt