Until we see a photo, I'm guessing it's an oil drain.
Standard on newer 3 liter MerCruisers, I just added one to my 1998 engine..
It replaces the oil pan drain plug and is long enough to extend through the
bilge drain. There is a plug in the end of the tube, connecting it with a
short chain, to the rear of the bilge drain plug.
What an easy way to change oil! On a warm engine, remove the drain plug and
pull it to get the oil drain hose outside the transom and into a bucket.
Then, undo the plug on the oil drain hose and let it drain.

"trainfan1" wrote in message
...
wrote:
I know it's not the dipstick tube, we pumped the oil / water our of the
dipstick tube when we winterized it.

It may be an oil drain kit like you said, but it doesn't line up with
the bilge drain plug at all. It comes out the side of the oil pan and
goes up, terminating in the wider section I tried to draw in ASCII.

We pumped the oil out with an electric pump through the dipstick tube
(my dad owns an auto shop, and is as puzzled by this tube as I am). I
did check the oil level, and it DID show over full. Color me an idiot


Thank you for your help. As long as the tube ISN'T a breather, I'm
guessing we can plug it with a piece of foam to keep water from pouring
into the oil pan (and spreading a lot of oil over the bottom of my
bilge compartment in the process).

BTW, any bets how long this motor will continue to run after being
lubricated with a 1:7 oil / water mixture for half a summer?


-Kyle

Water is not AS bad as glycol or DexCool... you might be OK... maybe use
Mobil 1 or Amsoil for the next season...

Post a pic, or several, of that tube, on your web space and someone here
will tell you what it is.

Rob