33 C.F.R. § 183.568
Each fuel line from the fuel tank to the fuel inlet connection on the carburetor must:
(b) Have an anti-siphon device or an electrically operated fuel stop valve:
(c) Provided that the fuel tank top is below the level of the carburetor inlet, be metallic fuel lines meeting the construction requirements of § 183.538 or “USCG Type A1” hose, with one or two manual shutoff valves installed as follows:
[CGD 74-209, 42 FR 5950, Jan. 31, 1977, as amended by CGD 81-092, 48 FR 55737, Dec. 15, 1983; CGD 85-098, 52 FR 19729, May 27, 1987]