The following is part of an email message I sent to a fellow powerboater in early '95. We were trading ideas on how to back a single-engine craft into a slip. This technique for coming straight back picks up at the point where you already have her lined up with the slip and her stern just ready to enter.
[This paragraph was added in May 2001 for those with a Krogen trawler. Before you start, go up to the flybridge helm and drive from there. Visibility aft is MUCH better than from the Pilot House. Also, use the upper deck as a "proxy" for the lower part of the boat and stern. It's DIRECTLY over the boat below, so if you "drive" the upper deck and position it corectly in the slip, the rest of the boat will be fine too! Now, let's proceed...]
"You'll get the hang of it. Here's MY secret. (discovered quite by accident) Clearly you have to plan ahead or do what's called "springing a pile" to get her more or less positioned correctly and lined up with the slip. That done, I turn the helm ALL THE WAY in the direction she wants to back due to prop torque. I do this rather than try to fight the torque effect for two reasons. (1) There's no way to counteract that effect with the rudder at low speeds no matter what you do because the rudder is almost completely ineffective at low speeds in reverse. (2) BECAUSE it's so ineffective, turning in the direction the boat naturally wants to back doesn't make it turn that way any faster.
Now, here's what you do. Give her a gentle amount of reverse to get her started moving backward. Then go back to neutral once she starts moving. (Remember, the prop torque effect only occurs when the prop is turning, so she'll go straight back by herself when she's in neutral.) She'll turn off course a bit, and you correct this with a QUICK burst of forward. Don't be timid about the burst. Because of the prop wash on the rudder, this has the effect of "hopping" the stern back into position without causing any forward motion. (If you have a little extra room, you can overcorrect some here to anticipate the effect of the prop torque during the next operation in reverse.)
Now you're ready to apply some more reverse. Repeat the process until she's all the way in. She goes back in a series of small arcs, but the result is a VERY professionally executed maneuver. Throughout this, I depend on the outer pilings to keep the bow from falling off downwind in the event of a fresh crosswind (which inevitably pops up out of nowhere just as the dock becomes lined with well-wishers and hecklers while you try to look "cool")."