Removed drain screw behind prop 2days ago to let unit drain. Today planned to dump some clean oil in resevoir and let it drain through before refilling with pump from bottom screw. When i went to add the oil to the resevoir my resevoir was still full at the same level it was 2 days ago when i removed the screw. Where should i start? Hose coming out of bottom of resevoir does not seem to be kinked to where it goes into the transom assembly.

Take the res off and dump it and most likely you will notice the Merc High perf green gear oil is a thick gel in the bottom of the res. It is preventing it to drain. That Merc gear oil gels thick over time and no one cleans the res out after gear oil changes so overtime it becomes really thick sludge / gel.

If this is not your case then your problem could be at the dribble valve, either its restricted or stuck or melted. The dribble valve is the valve with a tip on it when depressed drains the gear oil from the res, it is located between the bell housings and the upper outdrive. You have to pull the drive to get to it. I would pull the res first - dump the gear oil and see the condition of the bottom. very easy to figure out.

I might be stating the obvious but you didn't mention this, did you open the vent screw at the top of the drive as well?

Easy thing to forget to do. I 'know a guy' who did this once..... He's also poured five quarts of oil into the crankcase before replacing the drain plug...

Yes vent screw is open will mess around with it some more this weekend thanks guys

I do - at every change.

I'm not sure why it wouldn't be done, really.

Surely you removed the res cap as well. I would think so.