Honda BF15D BF20D Outboard Motors Shop Manual., Page 54Get this manual
Oil Change Drain the used oil while the engine is warmWarm oil drains quickly and completely1) Hold the outboard motor vertical2) Remove the oil filler cap and oil drain bolt, and drain the engine oil into suitable container
[I] OIL FILLER CAP
Please dispose of the used motor oil in manner that is compatible with the environmentWe suggest you take used oil in sealed container to your local recycling center or service station for reclamationDo not throw it in the trash, pour it on the ground, or down drainUsed engine oil contains substances that have been identified as carcinogenicIf repeatedly left in contact with the skin for prolonged periods, it may cause skin cancerWash your hands thoroughly with soap and water as soon as possible after contact with used engine oil
3) Make sure the O-ring is in good condition, replace it with new one if necessaryReinstall the drain bolt and the 0ring, and tighten the drain bolt securely