Oil in outdrive but passed pressure test

[dandoonan]

I have an 93 Chaparral 1900SL with a 4.3L V6 Alpa 1 Gen1. I had to replace the outdrive and now have a pre-Alph1.
When I drain the drive oil it was pure milk. I made up a test header and pumped it up to 12 psi. At first it keep dropping and I thought for sure I had a leak but then it stopped and has held over night. I'm had the outdrive sitting in a tub of water and no bubbles either.
The boat has been sitting in the garage for a almost 2 years due to other issues but I have now fixed them.
When I pull the drive the shaft couplers and bearing were all in good shape with no signs or rust.
I have seen it people respond differently on doing a vacuum test. Is this something the Merc states we should do?
I'm thinking about just reinstalling the drive, filling it and using it for a week or 2 then drain and re-check the oil. It probably wouldn't hurt changing oil that quick with as milky the oil was.
Has anyone ever heard of a pressure test being good but failing a vacuum test? If so is there a specific problem when this happens?
I would appreciate any and all help.

Thank you,

 

[alldodge]

Welcome
You have a leak just need to find out what seal.

Pressurize and then rotate each shaft drive, prop and shift. One or all of the seals is leaking. Vacuum test is a good test but keep it no more then 5 psi

 

[kenny nunez]

What you should do is drop the lower. Then you can pressure test the 2 units separately. You just have to plug the oil transfer port. There is a good chance the shaft seal area below the water pump base may be the leak as that is a water high pressure point. The shift shaft seal is also exposed to exhaust pressure also. This drive is older than the boat so it really needs close inspection. Quite often a drive will hold pressure but fail a vacuum test since some seals are back to back and the outer seal is damaged. A tight drive should hold at least 10-15 inches of vacuum and 10-15 lbs of pressure while doing as AD posted rotating he shafts.