I was speaking of cooling outdrives in general.

That little tube ain't so little. It provides enough water to cool a BBC.
The water jacket going through a Bravo is pretty large. I run a transom mount p/u for the engine as well. It used to flow water and dump out the side of the boat. When I put the new Imco on a few years back, I had the water jacket on th eside of the drive drilled and tapped. Now the water that goes through the drive feeds the drive shower and some excess dumps out the side.