Overhead-valve four-stroke engines run on 110-octane propane, and are eco-friendly with zero evaporative emissions, because propane, unlike gasoline, is not listed as a marine pollutant by the DOT. Propane is 50-times cleaner than gas, with 96% less carcinogenic compounds, 60-70% less smog-producing hydrocarbons and no Class I or II ozone-depleting chemicals. It s also domestically produced, reducing our dependency on foreign oil. LEHR outboards are easy starting with no choke and no priming, reliable with no carburetor gum-up or winterizing, economical because propane costs roughly half as much as gas. Convenient Twist n Go fueling on 5hp model. Simply twist in a standard 16.4oz. propane canister and start your engine no messy mixing or gasoline storage required. Or connect to a standard LPG tank with the provided 4' hose assembly for longer run times.