Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 371Get this manual
Oil Pump Outlet Check Valve Leak Test 1Disconnect both fuel lines (a) from AutoBlend Seal off outlet fitting (b)
3Draw eight inches of mercury (4 PSI vacuum)Check valves should not allow drop in meter readingIncrease vacuum to ten inches of mercury (5 PSI vacuum)Check valves should allow drop in meter reading Replace outlet check valves if requiredRefer to Oil Pump Outlet Check Valve Removal and Installation following