1983 Merc 25 hp leaking oil from water pump

[CV16]

I have some oil leaking from under the pump housing. No water at all in the oil though! I just bought the motor and put in a new impeller and noticed the oil. I drained the lower unit , no oil, and refilled it. I took it out for a test, ran sweet! I pulled the L/U just to check, more oil . No water in the oil still though. Will a complete pump replacement fix this? I've heard yes and no, so I figured I'd wait for a knowledgeable person from here to answer this.