Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 148Get this manual
FUEL JOINT, FUEL FILTER AND FUEL PUMP CHECKING THE FUEL JOINT
1Check: Fuel joint Cracksleakclogdamage
Replace
2Check: Fuel joint operation Impossible to maintain the specified pressure for 10 secReplace
Do not overpressurize the fuel jointExcessive pressure may cause air to leak outChecking steps: (1)Attach the mity vacMity vac: YB-3956-A90890-06756 (2)Apply the specified pressureSpecified pressure: 50 kpa (0.5 kgfcm2, 7.1 psi)