Hey everyone got a question about the lower unit on my 1984 Evinrude 70HP. I have noticed that there appears to be a knocking noise coming from the lower unit area of the engine underway only. Upon further inspection it looks like there is side to side play in the prop shaft, not very much just enough to feel it but not really see it. No water in the oil and it shifts and holds gear fine. Is this expected from a 30 year old engine or should I expect it to explode at any moment?