I have a 18' Tracker deep V hull, and a 20' Smoker Craft both with prop engines. I take them both all over the Snohomish and a lot of the Snoqualmie. You have to keep an eye out for shallow bars but you can make it around easily. It does help if you have power trim on the engine because when the water is low you can raise the engine a little and still make it through the shallower areas. Most of he shallow areas are on one side of the river and you can go around them on the other side. I can't think of any area off the top of my head that I can't make it up.
Paul