Just a minor point, but motors are not restricted to the flat water at WW at this time.
Not many folks in typical craft feel the desire to motor the rapids -- or the flats either, unless the wind is up. But every now and then a snout or something else really big goes down there and does the whole thing under power.
I say "at this time" because the wilderness study for the entire WW area might some day come to fruition, in which case motor use on the river might be impacted. Already, the land portion of the WW Wilderness Study Area is fenced off (the fence runs from east of Little Hole all the way to Big Hole) and mechanized travel of any kind has been banned.