1998-2006 Yamaha F20/F25 Outboards Service Manual, Page 79Get this manual
3Replace: Gear oil Replacement steps: Tilt up the outboard slightly Place container under the gear oil drain screw CD Remove the drain screw, the check screw (g), and then drain the gear oil Place the outboard in an upright position Add gear oil through the drain hole until it overflows from the check holeRecommended gear oil: GEAR CASE LUBE (USA) or Hypoid gear oil, SAE 90 Total amount: 320cm (10.8 US OZ, 11.3 Imp oz) Install the check screw and then the drain screwLower unit leakage check 1Check: Pressure Pressure drops Inspect the seals and componentsChecking steps: Connect the pressure tester to the gear oil level check holePressure tester: YB-0359590890-06762