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"  A 1-pound tank (1) that fits in the motor housing drives the engine for 1 hour to 90 minutes. A larger supply, such as a 20-pound tank (think backyard grill), runs in via an auxiliary port (2) and is good for at least a full day on the water. Fed through pressurized lines (3), the propane reaches the carburetor (4) as a vapor, making the Lehr less prone to flooding and fouling. The octane rating of propane is about 110, which provides for a high compression ratio (about 15.5:1, compared with about 14.7:1 in a gasoline outboard). This delivers power more efficiently to the crankshaft. * Because propane is not a solvent, it doesn&amp;#039;t break down an engine&amp;#039;s lubricating oils (the way gasoline does), which means greater engine longevity\u2014in theory, at least! "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/adventure/outdoors/a7987/how-an-outboard-motor-works-10951080/>