Are you sure your motor is a four-stroke and not a two-stroke? If it is a two-stroke, then you do not change the oil. You just replenish it as it gets used up from running the motor.
If it's 2 cycle, I think it'd be worth draining it and checking the pickup screen every coupla years. I've seen sludge build up in em, and an oil bottle seal getting in and floating around.
thanks guys for your reponds, sorry for not posted about 2-or 4 stroke I have a , 125 merc hp outboard 2 stroke year 2000 never drain tank ,boat was sitting for a year and before starting wanted to know if the oil tank has water from sitting