it is about a 5 hour trip of you just floated (no paddling). If you are in a kayak, and paddled some and stopped some, then i would plan on 5-6 hours.
I take that trip regularly, and I usually put in at the DAm at 730am, and usually hauling boats up the hill at Settles around 1:30
That's stopping at least once to eat some lunch and doing PLENTY of fishing from the boat while drifting.