Ok so I've got an 06' Merc 9.9 2S. Bought it used, was in great condition. Motor is running strong, starts and idles well. After a few trips and daily flushing, I noticed a buildup of a black, stick, almost grease like substance on the waterline in my flushing bucket. Has a thick consistency, almost like grease, and smells like fuel oil. I've been researching and learned that these 2 strokes are notorious for expelling unburned fuel/oil through the prop and causing a build up like this, but I wouldn't expect it to be this much. While checking this out I also noticed this same substance coming from a port that is on the shaft below the cowling. So just to be on the safe side I decided to drain my LU oil and check its condition. First thing is I don't believe there was as much gear oil as there should have been. I changed the oil about 5 myths ago. Second thing I noticed it is consistency,im Not sure if this is what's considered "milky" but I'll let the pics do the talking. I do believe it may be a prop shaft seal. And after talking with a Merc Tech, based on what I told him he agrees. What else may be causing this if not a prop seal? What else can I do to confirm this may be the problem? If it is a prop seal, can it be replaced without removing the LU? Thanks for any input or insight that can be provided.