Reading the shop manual for an OMC cobra outdrive (4.3 L, V6 engine)
the section re draining the outdrive oil has me confused:

There are 3 screws 1) a dip stick on the very top of the outdrive 2) a
fill port on the side of the OD about 1/2 way down 3) the drainport on
the very bottom of the OD.

To add oil the manual says if I remove the dipstick on the top and
then remove the lower plug at the drain port, only 1 tablespoon
"should" come out of the drain plug and a "hydraulic lock" will keep
the oil in the outdrive. It says to screw in the fitting from the oil
container and pump it until the oil is at the line on the dip stick.

But ...... it also says to drain and change the oil remove the dip
stick and the drain plug and all the oil will drain out.

What am I missing ? That makes no sense.
When I changed the oil I removed the lower drain plug and it ALL
drained out as expected.
I did not have quite enough oil and had to go to the boat shop.

When I followed the procedure to ADD a little more It made a mess
because much more than 1 tablespoon drained out. I got it up to the
correct level but it was pretty messy.

What am I doing wrong?

Kip