A vented fuel filler is installed in a boat from below the deck. The vented fuel filler comprises a body with an inlet portion. First and second grooves extend in arcs across the outer surface of the inlet portion upper end. Fuel and vent nozzles communicate with the inlet portion and the fuel tank. First and second clamps extend in arcs between opposite ends. The body inlet portion is inserted in a single, circular deck hole from below. The clamp inner edges are inserted into the body first and second grooves, and then the clamps are fastened to the deck. A cap has an annular array of teeth facing inward. A threaded insert has an annular array of teeth projecting outward. The insert teeth are received in the cap teeth, so that the cap can be selectively rotated. An inscription of "gas" will then be readable from the fuel dock by a dock attendant.