Lower Unit oil change blockage?

[MN Fats]

I have a 69 Mercury 20 horse. When I try and squeze the oil up from the drain hole nothing goes in. The chamber seems to be blocked not allowing the air and oil to move up to the top hole. What am I doing wrong?

PS- there wasn't much oil that drained, it was very milky too. Not a good sign, espescially on a lower unit that was replaced last year.

Thanks for the help.

[PierBridge]

Do you have the vent screw opened?

[Surface Tension]

This LINK should help.

[efgh]

On those older Mercurys, the vent screw is the phillips screw just below the motor flush plug if memory serves me right. Hope this helps you.