There are 4 main parts in a mechanical boat steering system – the helm (rotary, planetary or rack and pinion), bezel, steering cable, plus the connection kit (if required). The helm is a gearbox mounted in the vessel’s dashboard, to which the steering wheel & cable are connected. When you turn the wheel, it turns gears in the helm and moves the mechanical steering cable. This cable moves the engine through its steering arc, using a steering connection kit.
There are 3 types of helms:
1. Rotary Helm – is housed behind the instrument panel and converts the steering wheel movements into the push-pull action on the cable. This helm typically has one or two gears that mesh internally with a drum to move the steering cable. Rotary helms normally require quite a large round assembly behind the dashboard, so are more suitable for boats with larger dashboards & enough space behind them.
2. Planetary Helm – uses three or more gears that mesh internally with a drum to move the steering cable. This type of helm takes up less space than the rotary helm, so it is ideal for boats with small dashboards, or boats with lots of instruments installed around the steering wheel. However, it has more wear points than rotary helms.
3. Rack & Pinion Helm - fitted on the steering shaft, the pinion gear engages a rack gear in a tubular housing. This helm type offers less friction than a rotary helm and is an efficient system for moving the cable. However, they are wide and not suitable for many dashboards because of their larger size. They are ideal for boats with low dash panels that don’t have enough vertical clearance for a rotary helm. BAA does not currently sell rack & pinion helms as they are not commonly used in Australia.
The bezel is a piece of trim which is mounted on the boat’s dashboard. It covers the helm mounting hardware and provides extra support to the steering shaft.
A steering cable is a push-pull cable connected at one end to the helm, and the other end to the engine or rudder. It moves the engine or rudder in response to the steering wheel being turned. Single-cable steering is fine for boats with a motor of 130hp or less. More powerful engines such as a V6 motor on a high-performance boat (or those exceeding 80km/hr) should use a dual-cable steering system.
A connection kit is hardware that connects the steering cable to the engine or tiller arm. It can also connect the steering cable to the splashwell, or another mounting point. If the boat has more than one engine or rudders, it can also connect one engine or rudder to another.