1991 Johnson/Evinrude Models "EI" 40 thru 55 Service Manual, Page 79Get this manual
3Anti-Siphon Valvesafety standards require permanently installed fuel systems to have anti-siphon protectionThis protection can be afforded in two ways All fuel distribution lines must be secured above the highest fuel level when the boat is in its normal, unloaded, static floating position Each fuel pickup tube must have an anti-siphon valve installedAnti-siphon valves used must have pressure drop of no more than 2.5 inof mercury (Hg) at flow rate of 20 gallons per hourThe following OMC valves meet this requirementPIN 173273 for PIN 173274 for PIN 173275 for 5 16
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4Fuel Distribution Linesminimum inside diameter of 38 in(9,5 mm) is required for V6 and larger engines38 in(9,5 mm) is preferred for V4 and smaller engines, while minimum of 5 16 in(7,9 mm) is requiredDistribution lines must be USCG Type "A1" or "B1"Vinyl hose must not be used in permanently installed fuel distribution system5Fuel Distribution Fittingsall fittings must have minimum inside diameter of 14 in(6,4 mm), while in(7,1 mm) is preferred6Fuel Filterfuel filters must have pressure drop of no more than 0.4 inof mercury (Hg) at flow rate of 20 gallons per hourThe filter should have minimum filtered area of 200 square inches (1290 cm )