2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 69Get this manual
Periodic check and adjustment
3Check the oil for metal, discoloration, and its viscosityCheck the internal parts of the lower case if necessary4Insert gear oil pump or gear oil tube into the drain hole and slowly fill with gear oil until oil flows out of the check hole and no air bubbles are visible
Vacuumpressure pump gauge: (commercially available) 2Apply the specified pressure to check that the pressure is maintained in the lower unit for at least 10 seconds
CAUTION:
Do not over pressurize the lower unit, otherwise the oil seals can be damagedRecommended gear oil: Hypoid gear oil API: GL-4 SAE: 90 Oil quantity: 300 cm3 (10.14 US oz, 10.58 Imp oz) 5Install new gaskets and gear oil check screw 2, and quickly install the gear oil drain screw 1, and then tighten them to the specified torqueGear oil check screw and drain screw 1: Nm (0.9 kgfm, 6.6 ftlb) NOTE: Cover the check hole with rag when removing the vacuumpressure pump gauge from the lower unitLower unit holding pressure: 100 kPa (1.0 kgfcm2, 14 psi) 3If the specified pressure cannot be maintained, check the drive shaft, shift rod, Orings, and propeller shaft oil seals for damageIf necessary, check each shaft for bends and damage