Coil the hose tightly (about 8"diameter), and then take a short cable (12-15") with 2 eyes and wrap around the fuel hose and run another cable through the first one or through an eye. While not "totally" locked, one would have to uncoil the hose one wrap at a time making it a very unattractive and difficult target. The tighter the coil, the more trouble to uncoil and undo. Thread dinghy locking chain or cable through this eye, fuel tank, outboard etc.
