Pete Giordano, Priscilla Macy and I kayaked some of Mosby Creek 3/28/18. It is on private logging land, but permits can be obtained for the South Valley area which gives one access to this creek.
We paddled a 5.5 mile section starting at Lilly Creek (43.5791, -122.8649) and ending at a bridge near Allen Creek (43.6408, -122.9125). The beginning and end had quality class III bedrock slides and rapids, with one near the end being class IV. In the middle was a gravelly section with a couple logs to negotiate.
On the drive out we stopped to paddle a fun, roadside class IV chute against the left bank.
The flows for the day:
Coast Fork Willamette @ London was a good gauge too, but seems to have gone offline.
This resulted in a friendly, medium flow, more water would equate to more fun.