"kipmc4" wrote in message
...
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

The "hydraulic lock" will occur if only the lower drain is removed and the
other ports are tight in place. This prevents air from entering the drive
and replacing the interior volume from the drained oil, thereby stopping the
oil from draining. I've never owned an OMC Cobra drive, but here's how I
would do it. First remove the lower drain plug, leaving the other two ports
tightly covered. The hydraulic lock should minimize oil draining from the
port. Then attach the fitting from the oil container to the lower drain
port. Once connected, remove the dipstick on the top of the outdrive, then
pump enough oil into the bottom port to bring the level up to the
appropriate mark by repeatedly checking the level with the dipstick. When
done, replace the dipstick and tighten it securely to re-invoke the
hydraulic lock. Remove the fill attachment and quickly replace the lower
drain plug. That oughta do it. The manual you have was either poorly
written, or you read it wrong.