Oil leaking from raw water intake?

Did you keep the lower unit filled with gear oil all winter, or did you drain it? I can't tell by how you said you cracked it open, then you said you changed it mid spring. You are supposed to change the gear oil in the lower unit before you winterize it, the whole reason is to get any water or moisture out of there, and fill with fresh oil. Even a little moisture or water can freeze up and crack or expand gaskets.