You may be correct, that you're using a too-small hook for the weight of the yarn. Especially so if you're looking for a drapey (?) result. Single crochet is a pretty...ah...secure, non-draping stitch; if you'd like the scarf to be more drapey, double crochet (dc) would give you more of the desired effect, but you still need a good combination of hook size and yarn size.
What are you using right now with the sc?