46 CFR §143.260

1. (a)This section does not apply to an excepted towing vessel as defined in § 136.110 of this subchapter.
2. (b)To stop the flow of fuel in the event of a fire or break in the fuel line, a remote fuel shutoff valve must be fitted on any fuel line that supplies fuel directly to a propulsion engine or generator prime mover.
3. (c)The valve must be installed in the fuel piping directly outside of the fuel oil supply tank.
4. (d)The valve must be operable from a safe place outside the space where the valve is installed.
5. (e)Each remote valve control must be marked in clearly legible letters, at least 25 millimeters (1 inch) high, indicating the purpose of the valve and the way to operate it.