1990 Johnson Evinrude 120 thru 140, 185 thru 225, 300 HP, P/N 507875, Page 81Get this manual
6If you suspect the anti-siphon valve, perform these tests Remove anti-siphon valve from fuel tank and install adaptors and clear hose as shown Fill clear hose with water until "X" dimension is 20 in(500 mm)Water must not run through valve Increase water level until "X" dimension is 25 in(630 mm)Water must begin to run through valve before reaching 25 in(630 mm)7If your reading is less than inHg and air bubbles are visible in the clear hose, check entire boat fuel system for air leaksRemember, an air leak into fuel supply system might not create visible fuel leak8If your reading is less than inHg and no bubbles are visible, move the clear hose to the output side of the inline fuel filter Start engine and run at full throttle If bubbles appear, test inline fuel filter If no bubbles appear, go to Step 99If no bubbles are visible in Step 8, move the clear hose to the output side of the fuel distribution manifold Start engine and run at full throttle If air bubbles appear, test vacuum switchRefer to Vacuum Switch Servicing, this Section10If no bubbles appear in Step 9, remove the clear hose and install 0-15 PSI (0-103 kPa) fuel pressure gauge between pump and carburetorsOn V8 models, you must eliminate the fuel bypass valve from the fuel distribution system while performing system fuel pressure testAvoid pulling "E.S1763" fuel line off fuel fittingsPush off wherever possibleWhen removing "E.S1763" fuel line from fittings, carefully cut the hose to avoid damaging the fittings11Start engine and run at 800 RPM in gearAfter fuel pressure stabilizes, the pressure gauge must not indicate less than PSI (21 kPa) when held level with VRO hose fitting If pressure is less than PSI (21 kPa), test pulse hose and crankcase fittingRefer to VRO Component Servicing, this Section If pulse hose and crankcase fitting are good and prespumpsure is less than PSI (21 kPa), replace