Driving your boat in tight spaces

Even professional skippers can experience some anxiety when faced with a challenging close-quarters manoeuvre, no matter how many bow thrusters their vessel has or how many crew are at the ready.

Sooner or later, every boater will need to get their vessel in and out of a tight spot, be that in a marina, alongside a dock, or bow-first onto a riverbank. A good understanding of some fundamental concepts will help you master the art of close-quarters manoeuvring so you, too, can be confident in your approach.

When you push the throttle forward or astern, thrust is developed at the propeller in two ways. The most obvious is called axial thrust – that is the force that drives your boat forward or backward along the axis of rotation of the propeller.

Less recognisable is transverse thrust. This is the sideways force that the propeller exerts on the stern, particularly at low speeds or when stationary. It’s caused by the propeller’s clockwise or anticlockwise rotation in the water.

When viewed from behind, a propeller that turns clockwise in forward gear is called a right-handed prop. One that turns anticlockwise is a left-handed prop, which is less common in single-screw boats.

When you engage astern gear (reverse gear), a right-handed prop will tend to move the stern to port, while a left-handed prop will move the stern to starboard. This concept is very useful when you’re coming alongside a wharf or turning in a short space with a single inboard engine. 

An outboard motor or a sterndrive unit is a directional or ‘active’ rudder. This means that when you engage reverse gear, wherever you point it is the direction your stern will go. When you engage ahead, the opposite is true.

Remember this simple concept if you’re new to boating before randomly pushing the throttle back and forth hoping for the best. 

This technique utilises transverse thrust and is akin to a three-point turn in a car  … except, of course, it’s not a car, so there is more to it.

1. If you have a right-handed propeller, put the helm hard to starboard while making very slow headway. Keep the helm in this position throughout the manoeuvre.
2.  Apply a short burst of ahead power to kick the stern to port and gain some headway.
3.  As the boat gains headway, apply moderate revs in astern, but not enough to start going astern or to ventilate the propeller. The transverse thrust should kick your stern further around to port significantly.
4. Centralise the helm and drive off.

Because most single-screw boats have a right-handed propellor, they prefer to berth on the port side. This is because when in astern gear, the back of the boat will kick in towards the wharf very nicely with transverse thrust, especially while you’re going slightly forward and are approaching the wharf at an optimal angle of about 30 degrees.

Just before you reach the wharf, put the helm hard to starboard and engage astern gear with enough revs for you to notice that the transverse thrust is doing its job.

If you need to park starboard-side to a wharf, the transverse thrust will work against you and kick your stern away from the wharf when in astern gear. You can reduce this by maintaining a very slow approach to the wharf, gliding in at a shallower angle of around 15 degrees.

When you’re close to the wharf and almost stationary, give the boat a gentle ‘short burst ahead’ with the helm to port, to bring the stern in.