The origin of term comes from old boating practices. Before boats had rudders on their centerline, boats were steered by use of a specialized oar. This oar was held by a sailor located towards the stern (back) of the boat. However, like most of the rest of society, there were many more right-handed sailors than left-handed sailors. This meant that the right-handed sailors holding the steering oar (which had been broadened to provide better control) used to stand on the right side of the boat. The word starboard is a corruption of steering board, which in turn came from the old Norse language word stýri, in the language of the vikings. Similarly, the term for the left side of the boat, port, is derived from the practice of sailors mooring on the left side (i.e., the Portboard side) as to prevent the steering boards from being crushed. Because the words portboard and starboard sounded too similar to be distingued under windy sailing conditions, portboard was shortened to port. The starboad side of most naval vessels the world over is designated the 'senior' side. The officers' gangway or sea ladder is shipped on this side and this side of the quarterdeck is reserved for the captain. The flag or pennant of the ship's captain or senior officer in command is generally hoist on the starboard yard.

Most boats have a right turning propeller which pulls the right side up. Having the steering on that side will balance out the boat better. There are some boats that the propeller turns the opposite direction and will have the steering on the left. Newer boat designs have eliminated a lot of this but it still exists to some extent.

The location of steering controls is largely a matter of preference and specific design of a vessel. For example, on my 42' patrol ship the controls are on the left or port, possibly so the instruments and navigation equipment are more easily accessible on the right hand side of the operator, for more comfortable operation of controls on the radar, radios sounder and GPS recievers. Other than the steering controls the ship is a mirror image on either side, with twin engines, twin screw (left turning on starboard, right hand turning on port side), entrances, water tanks, fuel tanks, cleats and windows arranged in identical layout on each side. The only differences from side to side are minor things like the port engine charging a 12V system and PTO to bilge/fire pumps and the starboard running a 32V alternator. The ship is layed out symmetrically, but the entranceway to the forecastle located in the center of the steering house prevented the same design for the controls, necessitating the location off to one side. The fabricators likely flipped a coin to decide, or debated many points, but there is no general rule stating they must be on the right. Small craft which do not have center consoles like a bike are usually on the right, possibly so the throttles and gear levers can be operated by the dominant right hand of the predominantly right handed, and be mounted securely to the interior wall of the hull out of the way. Outboard motors usually come with the steering arm attached, protruding from the right hand side, and the steering and throttle cables, electrical wires and fuel lines all coming out a harness on the right. To install the console on the left would require either changing the engine configuration, or routing the harness through the right side and passing over to the left, requiring an exceptionally long harness in a circuitous semi-circular layout with very tight bends which are not conducive to the longevity of the hardware. Engine manufacturers likely stick to the one side to reduce the cost of designing the engines and maintain competitive pricing, likewise boat builders would need good reason to switch to the port side on outboard power, as it would increase building time and cost. The decision to make the side of choice, as another answer indicates, is likely the result of inertia resulting from archaic designs using the starboard side, while in modern craft center consoles are more prevalent in large ships, medium sized vessels could be either side, and small craft are predominantly oriented with the steering station on the starboard side. Many small craft and medium sized vessels are also increasingly incorporating center steering consoles, to balance loading and...center consoles on small craft allow the operator to straddle a seat, which is much more stable and better for absorbing impact and vibration, also in larger craft it allows for better visibility, particularly when docking or in close maneuvres on the 'off' side. Positioning the helmsman in the center gives them a better feel for what the vessel is doing, where it is and where it is going, it is all-round the best position and preferable for any craft which allows it by design. Often in rough seas I find myself standing off to the side of my steering station, in the center of balance of the ship, and operating it from the center even though it is located to the left of the wheelhouse. The following advice is offered with qualification and disclaimer: advanced pilotage in rough seas should not be attempted by inexperienced operators. The advice in this section will in no way equip the operator to deal with situations which might arise in rough water and though the information is accurate it is not intended to be educational, but is for entertainment only. The skills necessary to handle rough water can only be developed under supervised operation and practice in controlled and safe conditions. Notmrjohn, I guess I should add that in rough weather and small craft, at least in the vessels under 100 tonnes which I have operated, as much time is dedicated to running the throttles as steering, which is why in off-shore race boats there are two operators, a steering driver and a throttle man. Especially in very large following seas, the throttles must be opened and closed with every wave, as you crest a wave and run downhill, down the front of the wave, the throttle must be cut back to avoid pitchpoling or diving into the next wave in front of you, also as you pass through the bottom of the trough you must again apply power delicately and judiciously to accelerate up the back of the next wave you attack. Also heading into the waves throttling is important, as rogue waves and waves slightly higher or steeper than average necessitate slowing to prevent smashing out the windows and downflooding, or getting airborne off the crest, possibly landing on the face of the next wave, with the hull parallel to the face and little forward momentum, a situation very good at breaking boats, equipment or crew. Even in beam seas the throttle is worked constantly, to surf down a wave in the desired direction, yet avoid clapotic waves, the boat is either accelerated or slowed, to stay on the same wave and course, yet avoid the bigger waves and breaking waves by altering not direction, but speed. A good mariner in small craft can make a very smooth ride in very bad sea states by combining steering directions combined with throttle applications. Even in smaller waves the throttle and angle of attack can be manipulated so that the boat skips from the crest of one wave to the next, with the bow riding high and accelerating throughout the launch so the stern drops and the bow rises, the overall effect is the bow remaining relatively stationary and high, not slapping into the waves and causing rapid negative acceleration and jarring, while the waves slap against the aft section of the hull. Throttles must be adjusted often as wave heights, frequency and shape change due to variations in currents, shoals and wind. Operating the steering wheel with one hand is not a daredevil escapade, but a necessity, to free up a hand for operating the throttle. Not that all boat operators use these techniques, probably a lot less than the majority do, but for those very proficient at running in rough seas and making good time without damaging the boat, it is a finely tuned skill, the operation of steering and throttles together, particularly if there is more than one engine. I've been running down the face of a particularly large wave, with the wave pushing the stern ahead and sideways, the bow digging into the wave in front, trying to half broach, half pitchpole my boat, and the only thing that stopped it was putting one engine ahead and one in reverse with the rudders over to regain control, the entire sequence of events from the wave hitting to turning the rudder to compensate, reducing throttle on one engine to assist, increasing throttle on the other engine to have wash over the rudder to turn, reversing the other engine, applying throttle to the reversed engine, resuming normal operation by reversing all these steps, takes about 3-5 seconds. There's definitely no time for thinking things through or having second thoughts or hesitation of any kind, critical interventions must be performed in a timely and effective manner, as instinctive reactions as the result of developing these skills through use. Running in heavy seas is not for the inexperienced mariner, that is, not heavy seas as defined by the summer time recreational fisherman, but 40-60 foot breaking waves, or even smaller waves of 20 feet if they are extremely rough, close together and steep. It is somewhat similar to riding a bike, in that there are many who can ride a bike, or boat, but very few can operate it well enough to compete in moto x dirt bike races, or rough weather. While many of the less experienced dirt bike riders might be able to go around the track without incident, as many boaters go out in rough seas and survive, the difference between a couch potato driving a boat and a professional is just as pronounced as if a spectator jumped on a dirt bike and tried to compete in an actual race against professional racers. Jon Perryman writes "Most boats have a right turning propeller which pulls the right side up. Having the steering on that side will balance out the boat better. There are some boats that the propeller turns the opposite direction and will have the steering on the left. Newer boat designs have eliminated a lot of this but it still exists to some extent." While this answer is very close, I would like to point out that while the turning of the propeller to the right might cause the boat to tilt in the opposite direction, from transfer of angular momentum, while in transit the rudder redirecting the propwash typically compensates for this effect and balances the boat, except when becoming airborne, which requires turning the steering wheel just as you leave the water and back to center rudder as you re-enter the water. On outboards there is usually a fin shaped zinc anode on the underside of the cavitation plate which is used to fine tune this lateral thrust, not only reducing imbalanced forces on the steering system, but it also has that effect of balancing the boat if tuned correctly. On larger craft the rudder will simply be off center, or on the rudder indicator center rudder will not actually be center, but slightly off to whatever position keeps you straight and level. The direction of the spinning of the props is a valid point, though, but for a different reason. When reversing the engines the direction of the rotation has more effect on the movement of the vessel than reverse thrust. For example, while reversing a right turning propller it will tend to draw the stern to the right, as well as back. So, when at a dock it is preferable to put the left side in, since when you go astern it will pull you away from the dock, then when backing and filling the center of mass will be further from the dock when you go ahead with left rudder the bow will be further from the dock, allowing longer rotation before backing again with the net effect of drawing the entire ship away from the dock instead of the bow drifting into the dock as you stop backing and transfer the momentum into rotational movement with the forward w/left rudder. If you were to park with the right side in, you could still get off the dock, of course, it would just take more effort and you may even need to use springlines if there is even a slight wind or current pushing you onto the dock. This being the case, it is wise to place the helm where you can see the left side of the ship, since it will most often be toward the dock. (I might be wrong about the balance, but I'm pretty sure about the drawing away of the stern in the second part)

For small boats, the helm is on the right for better visibilty of the boats to starboard. In a crossing situation, the boat to starboard has the right of way.

1.)The Rules of the Road (COLREGS) require all vessels to keep to starboard (the right) when negotiating narrow channels and entrances. Having the steering position on the right-hand side allows for better visibility for judgement of clearances. 2.)Most skippers prefer to take advantage of the "paddle wheel effect" of right-turning propellers and come alongside "starboard side to" (right side against the quay).Therefore the wheel is placed on the right for better visibility of the (hard)quay/other vessel when the skipper is busy with the hazardous manoeuvre of coming alongside. Most engines are traditionally manufactured to turn clock-wise (to the right) when viewed from aft. The propeller is therefore right-turning and this causes a sideways force to the right (called transverse thrust) which helps the bring the boat over to the right. Tranverse thrust is also known as "prop walk" or "the paddle wheel effect" because the twist in the prop blades means they are scooping water to some extent from the right. On twin -screw boats they sometimes try to eliminate prop walk by using counter-rotating propellers. I am a navy coxswain.