Yamaha Marine Outboards Factory Service / Repair/ Workshop Manual 225G 250B L250B, Page 80Get this manual
FUEL PUMP
INSPECTING THE CHECK VALVE
E Inspect: Check valve operation Damagereverse air flow ReplaceInspecting steps NOTE: Do not overpressurize the check valveExcessive pressure may cause air to leak out(1) Install the Mity vac onto the check valve as shownMity vac YB-3595690890-06756 (2) Apply the specified pressure with the Mity vacCheck valve pressure 80 kPa (0.8 kgcm2, 11.4 psi) NOTE: Make sure no air comes out of the opposite side of the check valve