Lower unit leak or Crud in exhaust?

Hey guys, got a question about something I noticed while running my 1986 Johnson 15 hp on muffs today. I finally got the lower unit back together after replacing the outer prop seal. I then refilled with new oil and ran the motor on idle for roughly 5 minutes. Before that, it has been a year or so since the motor has run.

An hour later, I noticed this brown goop leaking from the prop. Is this unburned fuel/oil from the exhaust? Or did I botch the lower unit seal replacement? I drained about a tablespoon of oil out of the lower unit and it looked fine.

If its a through hub exhaust its normal if its not a through hub the prop shaft seals gone


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If you just changed the gear oil it would look blue/green if that it is the color type you used since you only ran it five minutes.I had a slow seep on the hub Oring on my 20hp and saw it by the bright green color of the oil in area leaking.

Exhaust is through hub. The oil I used is blue. Gonna go with this being from the exhaust. Thanks for the input guys. This is my first outboard and I think I keep looking for problems that may not be there.