You put the engine in reverse to back out of your slip, and instead of going straight back, the stern swings sideways toward the boat next door. That sideways kick is prop walk, and almost every single-engine sailboat has it. Fight it and docking feels like a lottery; understand it and it becomes one of the most useful tools you have in a tight marina.

Quick answer: prop walk (also called paddle wheel effect or propeller side force) is the tendency of a propeller to push the stern sideways as well as forward or back. It is strongest in reverse and at low boat speed. With a right-handed propeller, the stern walks to port in reverse; with a left-handed propeller, it walks to starboard. Once the boat picks up speed and water flows over the rudder, the rudder overpowers it.

What Is Prop Walk?

A propeller does not only push water straight back or forward. Because of the way it sits under the hull and the direction it rotates, it also produces a smaller sideways force that acts on the stern. When the boat is moving at speed, the rudder easily cancels this out and you hardly notice it. When the boat is stopped or moving slowly, and especially in reverse when the rudder is not in the propeller’s slipstream, the sideways force wins and the stern swings.

Propellers are described as right-handed or left-handed according to the direction they turn in forward gear, viewed from astern:

Propeller	Rotation in forward (from astern)	Stern walks in reverse	Stern walks in forward (slight)
Right-handed	Clockwise	To port	To starboard
Left-handed	Counterclockwise	To starboard	To port

Right-handed propellers are the more common arrangement on single-engine sailboats, but do not assume: engines, gearboxes and saildrives vary, so check your own boat.

Why It Happens

Several effects combine, and sailors argue happily about which one matters most. The two usually cited are:

• Shaft angle (asymmetric blade thrust). On a conventional shaft drive, the propeller shaft slopes downward toward the stern. Because of that angle, the blade moving downward meets the water at a slightly different angle from the blade moving upward, so one side of the propeller produces more thrust than the other. The result is a sideways push on the stern.
• Hull interference. The upper blades work close to the hull, where the water flow is disturbed and partly blocked, while the lower blades work in clear water. The propeller therefore behaves a little like a paddle wheel, pushing the stern toward the side the lower blades are moving toward.

In reverse the effect is exaggerated because the propeller is throwing its wash forward against the hull and keel rather than over the rudder, and the rudder has little or no flow to work with at low speed. That is why prop walk mostly shows up when you are backing out of a berth.

Finding Your Boat’s Prop Walk Direction

Never rely on a guess or on what the previous owner said. Spend ten minutes finding out exactly how your boat behaves.

Test in open water

1. Choose a calm day and a clear area away from other boats.
2. Bring the boat to a complete stop with the rudder centered.
3. Engage reverse at moderate revs and keep the wheel or tiller centered.
4. Watch which way the stern swings. That is your prop walk direction in reverse.
5. Try it again at different engine speeds, and note how much speed astern you need before the rudder takes control.

Test at the dock

With the boat securely tied up (good spring lines on both sides), put the engine briefly in reverse and look over the side for the prop wash. On many boats the wash shows up on the side opposite to the direction the stern will walk: wash on the starboard side means the stern walks to port. It is a quick check, but confirm it with the open-water test before relying on it.

Also note the strength. Some boats with saildrives barely walk at all; a long-keeled boat with a big three-bladed fixed propeller may walk so strongly that it cannot be steered in reverse until it has real speed.

Reversing a Sailboat Out of a Slip

Backing out of a slip is where prop walk causes most of the damage, and also where a little planning pays off.

• Plan the turn around the kick. If your stern walks to port and you need to turn to port once clear of the slip, prop walk is helping you. If you need to turn the other way, you may need to back out straight, stop, then motor forward into the turn.
• Set up for the walk. Before engaging reverse, angle the boat (with lines or by position in the berth) so that the expected sideways kick takes the stern into clear water, not into the neighbor’s bow.
• Use a decisive burst, then neutral. A short, firm burst of reverse gets the boat moving astern. Then shift to neutral: the prop walk stops, and the boat carries way. Once you have a knot or two of sternway, the rudder starts to work and you can re-engage reverse gently.
• Hold the helm firmly. In reverse, the rudder is pushed hard by the water flow. Keep a firm grip on the wheel or tiller and avoid big sudden movements.

Wind matters too. In a crosswind, the bow will often blow off faster than the stern walks, so time the move for a lull and get the boat moving quickly. Our guide to sailing maneuvers including docking has more on close-quarters handling.

Using Prop Walk to Dock and Turn in Tight Spaces

Choose your docking side

When you come alongside a pontoon and give a burst of reverse to stop, prop walk will pull the stern sideways. With a right-handed propeller, the stern goes to port, so coming in port side to means the brake also draws the stern neatly in against the dock. Starboard side to, the same burst kicks the stern away from the dock, so approach at a shallower angle and use less reverse, or get a stern line ashore first.

The back-and-fill turn

A back-and-fill (sometimes called a three-point turn under power) lets you spin a single-engine boat almost in its own length. With a right-handed prop, it works best turning to starboard (clockwise):

1. Put the helm hard over to starboard and leave it there for the whole maneuver.
2. Give a short, firm burst ahead. The prop wash over the rudder pushes the stern to port and the bow swings to starboard, before the boat builds much forward speed.
3. Shift to neutral, then give a short burst astern. Prop walk kicks the stern to port again, so the bow keeps swinging to starboard while the reverse cancels the forward motion.
4. Repeat until the boat is pointing where you want. Keep the bursts short so the boat pivots rather than travels.

With a left-handed prop, do the same turning to port. Try it in open water first; it is much easier to learn when there is nothing to hit.

Stern-to and Med mooring

When you reverse into a stern-to berth, prop walk can either help or ruin the approach. Most skippers start the reverse run with the stern offset to allow for the kick, and gain sternway early so the rudder bites. We cover this in detail in our guide to Med mooring.

Picking up a mooring or stopping

Prop walk also matters at night, when depth perception is poor and you rely on precise, slow maneuvers; see our night sailing tips for arriving after dark. It matters whenever you use reverse as a brake, for example when coming up to a mooring ball. A burst of reverse swings the stern one way and the bow the other, so choose the side you pick up the ball on accordingly. See our step-by-step guide on how to pick up a mooring ball.

Reducing Prop Walk

You can rarely eliminate prop walk, but several things affect how strong it is:

• Drive type. Saildrives and propellers on a nearly horizontal shaft generally walk less than a conventional shaft drive with a steep shaft angle.
• Propeller type and size. Blade area, pitch and number of blades all change the effect. Fixed, folding and feathering propellers each behave differently in reverse, and some feathering designs allow the pitch in reverse to be adjusted. Our comparison of fixed vs folding vs feathering propellers goes into the trade-offs.
• Throttle technique. Short bursts of moderate revs produce less walk than holding high revs in reverse. Getting the boat moving and then using neutral is often the cleanest approach.
• Speed. The faster the boat moves through the water, the more authority the rudder has. Prop walk is mostly a low-speed problem.

If prop walk on your boat seems unusually strong or has changed, have the propeller checked. Damage, fouling or the wrong replacement propeller can all change how the boat handles. For engine choices on new or repowered boats, see our overview of inboard boat engine brands.

Prop Walk: Summary

Prop walk is the sideways push on the stern caused by the propeller, strongest in reverse and at low speed. A right-handed propeller walks the stern to port in reverse, a left-handed one to starboard. Test your own boat in open water, plan your berths and turns around it, use short bursts of throttle and neutral rather than long runs at high revs, and pick your docking side so the kick works for you. This is especially worth doing at the start of a bareboat charter, when the boat is new to you. Once you can predict it, prop walk stops being a nuisance and becomes the tool that lets you spin a boat in a crowded marina. And when there is no engine at all, our guide to how sailboats move without wind looks at the alternatives.