5h 11m 39s
I ran the South Section of the Lost Coast last October in 5:11:39, from Usal Campground to Needle Rock. I had some trouble following the trail in the first couple miles but then ran more cautiously and was fine. My watch registered 18.05 mi with 5,791 ft of gain in 4:14:23 of moving time.
Briceland Rd was closed so Needle Rock was the best stopping point. If you can convince someone to do the drop/drive for you, this is an excellent section of path to explore. I hesitate to call it a trail due to the primitive nature.