CAT 3306 Crankcase pressure?

Hi all, I'm really new to the forum. I work on an oystering boat, and our main engine is a CAT 3306. Today when adding oil, the oil bubbled back up into the funnel, and drained slowly back into the engine. Then we checked the CCV, and found that the line (1.5" line to a filter box) was plugged full of an oily/watery sludge, about the consistency of wheel bearing grease. Haven't checked the filter yet but I'm assuming it's plugged as well.

Obviously the plugged CCV caused the pressure, but...

CAT 3306 Crankcase pressure?

CAT 3306 Crankcase pressure?