..and not the kind you drink!

Every time I yank the power head off my older Merc triple I see a whitish, ugly looking layer of...stuff. I'm wondering if this is common (and okay) since this motor has a pocket below the lower bearing housing where the...stuff can build up.

The early Merc triples are similar to the big fours and in-line sixes in that they also have this "pocket" below the power head.

Are you guys also seeing this when you pull your PHs off?