Because boat engines may backfire, all powerboats (except outboards) that are fueled with gasoline must have an approved backfire flame arrestor on each carburetor. Backfire flame arrestors are designed to prevent the ignition of gasoline vapors in case the engine backfires.
- Two types of backfire flame protection systems are acceptable:
- A backfire flame arrestor on each carburetor. Flame arrestors must be approved by the USCG (must comply with SAE J-1928 or UL 1111 standards) and be marked accordingly. Periodically clean the flame arrestor(s) and check for any damage.
- An arrangement of the carburetor or engine air induction system that safely disperses any flames from a backfire to the atmosphere outside the vessel.
- Paper or automotive filters are not USCG–approved and are dangerous to use.