It's the Law: Required Equipment for Your Vessel

Ventilation Systems

• All gas-powered vessels with closed construction that would entrap fumes must be equipped with a ventilation system to remove explosive vapors from the bilges of engine and fuel tank compartments. Explosive vapors are heavier than air and accumulate in the bottom of the vessel without proper venting, creating an extremely hazardous condition.
• Montana law requires at least two ventilation intake ducts fitted with cowls or their equivalent to remove fumes from bilges and fuel tank compartments.
• If your vessel is equipped with a power ventilation system, turn it on for at least four minutes after fueling, prior to starting your engine. If not so equipped (such as PWCs), open the engine compartment and sniff for gasoline fumes before starting the engine.

Backfire Flame Arrestors

Backfire flame arrestors are designed to prevent the ignition of gasoline vapors in case the engine backfires.

• Every inboard gasoline engine must have an Underwriters Laboratory–approved backfire flame arrestor in proper working order that is securely attached to each carburetor.

Mufflers and Noise Limitations

In Montana, all motorboats must be equipped with an underwater exhaust system or muffler system to limit engine noise.

• Motorboats and PWCs may not emit noise in excess of 86 decibels measured at a distance of 50 feet. At “idle speed,” exhaust noise may not exceed 90 decibels when measured by a sound meter held one meter (about three feet) from the muffler
• . More restrictive noise standards are in effect for Flathead Lake (Flathead and Lake Counties), Echo Lake (Flathead County), and Swan Lake (Lake County) in northwestern Montana because of population density and heavy recreational use. On these waterways, noise near the shoreline may not exceed 75 decibels.
• Certain exceptions are made for state-sanctioned regattas or boat races and by special permit.