I installed a new prop same size and pitch as the old one. Since the old one a chunk nocked out of the edge I figured a new one would be better balanced. After installing it, I get a distinct whine at certain rpms (i'd say from 1/3 to 1/2 throttle). Faster rpms and it goes away. I did not have this noise with the old prop. I'll check my lower unit oil, but I replaced it a couple of months ago. Could it be a shaft bearing? It goes away completely at low and high rpms.