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31 Chapter 4 ■ Backfire Flame Arrestors Because boat engines may backfire, all powerboats (except outboards) that are fueled with gasoline must have an approved backfire flame arrestor on each carbu- retor. Backfire flame arrestors are designed to prevent the ignition of gasoline vapors in case the engine backfires. ◆ Backfire flame arrestors must be: • In good and serviceable condition • U.S. Coast Guard–approved (must comply with SAE J-1928 or UL 1111 standards) ◆ Periodically clean the flame arrestor(s) and check for any damage. Ventilation Systems Ventilation systems are crucial. Their purpose is to avoid explosions by removing flammable gases. Properly installed ventilation systems greatly reduce the chance of a life-threatening explosion. ◆ All gasoline-powered vessels, constructed in a way that would entrap fumes, must have at least two ventilation ducts fitted with cowls to remove the fumes. At least one exhaust duct must extend from the open atmosphere to the lower bilge. At least one intake duct must extend from a point at least midway to the bilge or below the level of the carburetor air intake. ◆ If your vessel is equipped with a power ventilation system, turn it on for at least four minutes in either of these situations: • After fueling • Before starting the engine ◆ If your vessel is not equipped with a power ventilation system (for example, a personal watercraft), open the engine compartment and sniff for gasoline fumes before starting the engine. Mufflers and Noise Level Limits Excessive noise can prevent a vessel operator from hearing signals and voices. ◆ The exhaust of every internal combustion engine on any vessel must be effec- tively muffled. That is, the engine's exhaust must be muffled or suppressed at all times so as not to create excessive noise. ◆ It is unlawful to operate a vessel that exceeds a noise level of 96db when measured at 100 feet while the vessel is traveling on plane. ◆ The use of cutouts is prohibited. Vessels built after July 31, 1980, which contain power exhaust blowers in gasoline engine compartments, must have the above warning sticker placed near the instrument panel. WARNING: Gasoline vapors can explode. Before starting engine, operate blower for four minutes and check (using your nose) engine compartment for gasoline vapors. backfire Explosion of prematurely ignited fuel or of unburned exhaust gases in an internal combustion engine Powerboats are built to ventilate the engine when underway. As the boat moves along, an air intake scoops up fresh air and forces it down the air duct into the engine compartment. The exhaust sucks out the explosive fumes from the lowest part of the engine and fuel compartments. cowl Hooded opening designed to scoop in air Copyright © 2014 Boat Ed, www.boat-ed.com

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