What the boat changes

Two yachts of the same length can handle very differently in harbour. Where the propeller sits, how many rudders there are, the shape of the keel, the helm and the bow thruster all change what works and what doesn’t.

Shaft drive or saildrive

With a shaft drive, the shaft leaves the hull at an angle, often around 15°, and the propeller sits well aft, just ahead of the rudder. With a saildrive, a vertical leg passes through the bottom of the boat and the propeller shaft is horizontal, closer to the middle of the boat.

What it changes:

Prop walk is stronger with a shaft drive; a saildrive reduces it markedly. See Prop walk.
Prop wash over the rudder. With a saildrive propeller well forward of the rudder, handling under power can suffer; other owners still use the wash from a burst ahead to steer. It depends on the boat.

Single or twin rudders

With a single rudder, the propeller is just ahead of the rudder. A burst ahead throws water over it: the boat turns before she has even picked up speed.

With twin rudders, the propeller sits between the two rudders and its wash passes between them with almost no effect. As a result:

from a standstill, it is practically impossible to start a turn with a burst of throttle;
steering depends on way alone: you need a longer burst of throttle to gain enough speed, and a little more throttle astern than with a single rudder;
once moving, these modern short-keeled boats turn as tightly as a single-rudder boat, even at low speed;
many larger twin-rudder boats have a bow thruster to make up for it.

See Carrying way.

Long keel

A long keel has a lot of draught aft and less towards the bow. Going ahead, this helps the boat hold her course; going astern, it does her no favours at all. These boats go astern very badly under power, have a large turning circle and are known as “tricky in harbour”. By contrast, a flat-bottomed hull with a bolted-on fin keel and a spade rudder steers almost as well astern as ahead.

Some long-keel owners say they have no directional control at all astern; one of them nevertheless finds the track predictable over a boat length. They rely mostly on prop walk and on firm, decisive use of the engine.

Tiller or wheel

Which way. With a tiller, you push it away from the direction you want to turn; with a wheel, the boat turns the way you turn the wheel.
Going astern, the water tries to slam the rudder hard over as soon as it leaves the centreline. One owner doubts that a short tiller gives enough leverage to keep control astern: hold it firmly.

Bow thruster

A bow thruster pushes the bow sideways without needing any speed. Its limits:

it is only really effective when the boat is stopped or doing less than a knot;
once the wind has blown the bow off, many are not powerful enough to bring it back up to windward;
an electric thruster can only run for a short time before it overheats or cuts out: use it in short bursts, with pauses;
when the bow goes one way, the stern goes the other;
it works best mounted deep and well forward; on a yacht where space is short, it has to be more powerful.

Pitfalls

Treating an unfamiliar boat like the one you know. Before entering harbour, try her out in open water: which way she walks, how she answers a burst of throttle, how much speed she needs astern.
Relying on a burst of throttle with twin rudders: the boat moves forward but won’t turn until water is flowing over a rudder.
Learning with the thruster only: learn to manoeuvre without it first.