Yup, looks like a black racer. The ones I usually see are about 3', but that one looked to be about 5'. I saw one outside my back door a few months ago that was about 4'. They seem to be quite shy and will avoid you if at all possible. If you want it to go away then just go down there making lots of noise as you approach, and make sure there's lots of clear getaway room for him. Mine disappears under the overgrown azalea bushes along the back of my house.