It's quite a ways from MB to the Outer Banks if you go that route. Once you get up into NC and up to Manteo/Nags Head, it's another hour to hour and a half down the island to the Hatteras Ferry, then it's a 45 min. ferry ride over to Ocracoke. You might be better off driving from MB up the coast, and taking the Cedar Island Ferry (I think it's a 2 hour ferry and must be booked in advance) from the Morehead City, NC area. That ferry takes you to Ocracoke.
We live just north of Charlotte, NC and it takes us like 4 hours to get to Myrtle Beach from our house. It takes us 6 hours to get to Avon (just north of Hatteras) on the Outer Banks (just got back again last week) we LOVE the Outer Banks and Ocracoke. Would definitely recommend a trip out there. But we have to stay a week, a couple days wouldn't do it for us
I mapquested it for you.... it's 6 hours and it takes you the way I recommended...the Cedar Island Ferry...
Driving Directions from Myrtle Beach, SC to Ocracoke, NC