The steering system on a sailboat is composed of sub-systems including pieces such as the cable, rudderpost, and rudder itself. The propulsion system includes parts such as the propellor and stuffing box.
Four types of steering are usually seen. The most popular by far is cable steering. This consistes of wire cables that rotate the rudderpost via a radial or quadrant. A quandrant is used if the binnacle and rudderpost do not line up. Otherwise, simply a radial is used. An old fasioned alternative is worm gear steering. Another is rack and pinion steering. These geared types are only seen on older large vessels such as tallships where you have to control a large rudder. A newer alternative to cable is hydraulic steering. Hydraulics easily installs and can coordinate with an autopilot and inside steering easily.
The rudder post is the where the rudder connects to the steering. This connection can be a source of trouble on boats. The simplest, most inexpensive alternative is a grease joint. Next in cost are plastic bushings to lubricate the post. The best choice is stainless bearings which last the longest and are the least likely to fail.
A rudder is connected to the rudderpost and directs the boat. Rudders are made of either foam or solid laminate. With foam, the rudder can get saturated and expand and contract cracking or splitting the rudder. With solid fiberglass, the same can occur but is less likely. Fiberglass rudders blister and split at their joint between the two halves that make up the rudder.
The shaft from an inboard engine goes through a stuffing box or valveseat to reack outside. The stuffing box is the most common source of leaks on a boat. A valveseat is an alternative, less common avenue to block the leaks around the shaft. The valve seat does not use packing material but just a rubber shape.
A propellor is at the end of the shaft and with blades spins to move a yacht. Propellors are either fixed, folding, or feathering. A fixed prop has 2 or 3 blades and is simply welded together, bronze. A folding prop has blades which fold back hydrodynamically to leasen drag. The feathering prop has blades which twist to become hydrodynamic.
The steering system and propulsion systems work together. The above sections describe the mundane sub-parts of these systems which help direct and propel a yacht to dreamy destinations.