1982 150 Mariner xr2 water coming from fitting on engine

I just purchased this unit and was told it needed a new impeller. After I replaced the impeller I had the cowling off, started it up and no water was coming out of the discharge, but water was coming out of a fitting on the top of the motor. This was discharging water into/under the cowling.
This fitting has no or seems to have had no hose coming out. No idea??
Attached is a picture of the fitting on the top of the motor. Any help on what I need to do with this would be great. I have searched every diagram I can find and nothing shows this part of the engine.

That is a fitting for a water pressure guage… did you run a compression test before buying as that motor looks to have gotten way hot sometime in it life.

Thank You!
Well...supposedly he said the compression was good, but I have already found things that weren't disclosed.
It runs smooth at all rpm's that we have run it and seems to perform well in all the situations I have put it through.
For what I paid, I'd be good even if I had to rebuild the engine.
Thanks again!