---

I should have mentioned that one of the first items I checked was the cap. I detected no leak around the cap. That cap, by the way, screws in several turns for an extraordinarily tight seal. As has been pointed out, that tank system works because of pressure. There was no evidence of any escaped fuel on top of the tank.
Local store was advised of the tank failure, as well as the catalog website.
By the way, I usually have good experiences with West Marine products. This is the first WM product problem I have had over years of ownership of sailboats, trawlers, and now, an outboard.