A backfire flame arrestor is a piece of safety equipment that you need to keep onboard if your boat has an inboard engine.
When a boat engine backfires, flames could come into contact with fuel or other flammables and start a fire. A backfire flame arrestor is a round device with a grill that you attach to the air intake with a flame-tight connection, to stop flames from threatening your boat by diverting them to the surrounding atmosphere.
Since 1940, backfire flame arrestors have been required on boats with inboard motors, but not just any equipment will meet established safety standards. Your flame arrestor must be approved by the U. S. Coast Guard and either the Underwriters Laboratories (UL 1111) or the Society of Automotive Engineers Standard (SAE – J1928 – 2012). These rules apply to motorboats, but may differ depending on the type of boat engine you have installed.
Equipment maintenance is an important element of boater safety. Inspect and clean your backfire flame arrestor once a month as part of your fire extinguisher maintenance. Check for damage, including holes, and make sure there is no oil or gas in the grid. If necessary, remove the flame arrestor and clean it with soap and water. Let it dry completely before reinstalling.
Make sure the arrestor is firmly attached to the carburetor, and that it has a flame-tight connection.
In addition, you should have your backfire flame arrestor inspected by a knowledgeable person at least once a year to confirm that it is working properly.