The past two times I've use the boat when I went to back the boat off the trailer the lower unit made a knocking noise when I put the motor in gear. After putting back in neutral a couple times it stopped. On both occasions I ran the boat all day and never had any other issues. I checked and changed the lower unit oil today and the oil looked fine other than some very minute swirls mixed in. There was a small amount of very fine metal "dust" on the tip of the magnetic drain screw but now shavings or pieces. Any ideas what the knocking is about and why does it do it and startup once or twice then go away?
