SD60 oil leak

[Captain Bill]

I've got a problem with one of my SD60s that has me and the mechanic stumped. The gear case was recently replaced due to a defect and the unit has developed a oil seep out of the forward water intake. The seep seems to be intermittent. I am hesitant to splash until The issue is solved. The gear case was replaced late last month. We had some additional work too be completed before splashing so we had some time before we were to splash. About a week after the reinstall had been completed I found a thin streak of oil emanating from the forward water intake. I informed the mechanic that we were going out of town for wedding and he could have access to fix it while we were gone. When he got there he says he saw no leak and no oil, but pressurized it to 2 psi . Still no leak. He then pressurized it to 8 psi and still no leak. I get back on the 18th of the month and no leak. I put on anti foul and watched it for a solid week. Pressure held at 8 psi and still no leak. Two days later I go to reinstall the prop in preparation for splashing and the oil seep is back. In the meantime It had gotten much colder (45f 8C) at night and the pressure had dropped to slightly below 8 psi, but with the temperature drop that makes sense. As far as I can tell there are only three O-rings where the oil can get to the water passage. In my experience when there is pressure on one side of a leaking O-ring they don't seep slowly. Does anyone have an experience where an O-ring under pressure just seeped? The amount of oil is minuscule, but since this is below the waterline I fear where oil can get out water can get in. In the meantime I'm stuck in NC on the hard while winter approaches.