I went to change my lower unit oil and removed both top and bottom plugs. Nothing came out! Thinking it was dry, I started to add oil to the bottom plug. A black sludge starting coming out the top. I continued to fill until all the sludge came out and the oil started flowing freely out the top plug. There was quite a bit in there.

As I type this I realize it was only about 45 degrees in the shop. Could that be the culprit, or is something else going on? Another thing I thought was maybe too much grease was added to the grease ports??? The motor only has 56 hours on it. Thoughts????

Yep

You are trying to change 90w oil that is probably the consistency of cane syrup.

Sit you space heater there by the lower unit for a few hours then try and change it.

I'd like to ask another question about gear oil but the all-knowing River would chime in with his "expert" opinion.

Ahhh what the hell, anyone know anything about Alisyn Pro Gear Lube? I heard it's good stuff. Stuff is zero weight but supposed to be good stuff.