The day I took delivery of my first boat (Hunter 280), my boys were helping me fuel it up at the marina where I bought it. One of them (name withheld to protect the innocent), unscrewed the cap and let it hang by the chain…but the chain wasn’t attached to anything, and the cap promptly dropped into the water. The fuel guys tried to find one, the broker checked the ships store and no luck. Nothing fit. Finally, the broker ”borrowed“ one from another Hunter he was selling…got us underway and out of his hair.
No idea what size the Catalina uses.
Greg