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86-427: In order to eliminate the chances of hitting bottom with an outboard motor, the motor can be tilted up to an elevated position either electronically or manually. This helps when traveling through shallow waters where there may be debris that could potentially damage the motor as well as the propeller . If the electric motor required to move the pistons which raise or lower the engine is malfunctioning, every outboard motor

172-467: A weed hatch over the propeller, and once the narrowboat is stationary, the hatch may be opened to give access to the propeller, enabling debris to be cleared. Yachts and river boats rarely have weed hatches; instead they may fit a rope cutter that fits around the prop shaft and rotates with the propeller. These cutters clear the debris and obviate the need for divers to attend manually to the fouling. Several forms of rope cutters are available: A cleaver

258-419: A better match of angle of attack to the wake velocity over the blades. A warped helicoid is described by specifying the shape of the radial reference line and the pitch angle in terms of radial distance. The traditional propeller drawing includes four parts: a side elevation, which defines the rake, the variation of blade thickness from root to tip, a longitudinal section through the hub, and a projected outline of

344-434: A blade onto a longitudinal centreline plane. The expanded blade view shows the section shapes at their various radii, with their pitch faces drawn parallel to the base line, and thickness parallel to the axis. The outline indicated by a line connecting the leading and trailing tips of the sections depicts the expanded blade outline. The pitch diagram shows variation of pitch with radius from root to tip. The transverse view shows

430-541: A boat out of the hole and onto plane. Ole Evinrude Ole Evinrude , born Ole Andreassen Aaslundeie (April 19, 1877 – July 12, 1934) was an American entrepreneur, known for the invention of the first outboard motor with practical commercial application. Ole Evinrude was born in Hunndalen in the municipality of Vardal (now Gjøvik ), in Oppland , Norway . The Evinrude surname, which he adopted in

516-454: A closed-loop cooling system with a heat exchanger. This means saltwater is not pumped through the engine block, as is the case with most outboard motors, but instead engine coolant and outside water are pumped through (opposite sides of) the heat exchanger. An outboard engine may stall if it does not have the correct inputs. Common problems that lead to stalling are electrical issues, low quality gas or clogged fuel filer. Other issues may include

602-430: A conventional propeller. The frame that holds the motor has a short, swiveling steel pin/tube approximately 15 cm long underneath, to be inserted into a corresponding hole on the transom, or a solid block or wood purposely built-in thereof. This drop-in arrangement enables extremely quick transfer of the motor to another boat or for storage – all that is needed is to lift it out. The pivoting design allows

688-489: A damaged carburetor oil switch. In Vietnam and other parts of southeast Asia long-tail boats use outboard motors altered to extend their propellers far from the rest of the motor. In Vietnam these outboards are called máy đuôi tôm ( shrimp tail motor ), which are smallish air-cooled or water-cooled gasoline, diesel or even modified automotive engines bolted to a welded steel tube frame, with another long steel tube up to 3 m long to hold an extended drive shaft driving

774-687: A different method of DI. Fuel economy on both direct-injected and four-stroke outboards measures from a 10 percent to 80 percent improvement compared with conventional two-strokes. However, the gap between two-stroke and four-stroke outboard fuel economy is beginning to narrow. Two-stroke outboard motor manufacturers have recently introduced technologies that help to improve two-stroke fuel economy. In 2012, Lehr inc. introduced some small (<5 hp) outboards based on modified Chinese petrol engines to run on propane gas. Tohatsu currently also produces propane powered models, all rated 5 hp. Conversion of larger outboards to run on Liquified petroleum gas

860-508: A ducted propeller. The cylindrical duct acts as the stator, while the tips of the blades act as the rotor. They typically provide high torque and operate at low RPMs, producing less noise. The system does not require a shaft, reducing weight. Units can be placed at various locations around the hull and operated independently, e.g., to aid in maneuvering. The absence of a shaft allows alternative rear hull designs. Twisted- toroid (ring-shaped) propellers, first invented over 120 years ago, replace

946-514: A machinist while working at various machine tool firms in Milwaukee , Pittsburgh , and Chicago . In 1900, Evinrude co-founded the custom engine firm Clemick & Evinrude. In 1907, he invented the first practical and reliable outboard motor , which was built of steel and brass, and had a crank on the flywheel to start the two-cycle engine. In 1907 he had built his first gasoline-powered outboard motor, and two years later, Evinrude Motor Company

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1032-400: A marine screw propeller is based on a helicoidal surface. This may form the face of the blade, or the faces of the blades may be described by offsets from this surface. The back of the blade is described by offsets from the helicoid surface in the same way that an aerofoil may be described by offsets from the chord line. The pitch surface may be a true helicoid or one having a warp to provide

1118-429: A pin called a topper tilt lock. Ventilation is a phenomenon that occurs when surface air or exhaust gas (in the case of motors equipped with through-hub exhaust) is drawn into the spinning propeller blades. With the propeller pushing mostly air instead of water, the load on the engine is greatly reduced, causing the engine to race and the propeller to spin fast enough to result in cavitation , at which point little thrust

1204-473: A pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft with an approximately horizontal axis. The principle employed in using

1290-501: A propeller's forward thrust as being a reaction proportionate to the mass of fluid sent backward per time and the speed the propeller adds to that mass, and in practice there is more loss associated with producing a fast jet than with creating a heavier, slower jet. (The same applies in aircraft, in which larger-diameter turbofan engines tend to be more efficient than earlier, smaller-diameter turbofans, and even smaller turbojets , which eject less mass at greater speeds.) The geometry of

1376-542: A row boat across Yarmouth Harbour and a small coastal schooner at Saint John, New Brunswick , but his patent application in the United States was rejected until 1849 because he was not an American citizen. His efficient design drew praise in American scientific circles but by then he faced multiple competitors. Despite experimentation with screw propulsion before the 1830s, few of these inventions were pursued to

1462-416: A rubber bushing can be replaced or repaired depends upon the propeller; some cannot. Some can, but need special equipment to insert the oversized bushing for an interference fit . Others can be replaced easily. The "special equipment" usually consists of a funnel, a press and rubber lubricant (soap). If one does not have access to a lathe, an improvised funnel can be made from steel tube and car body filler; as

1548-408: A screw propeller is derived from stern sculling . In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the water at the effective angle. The innovation introduced with the screw propeller was the extension of that arc through more than 360° by attaching the blade to a rotating shaft. Propellers can have a single blade , but in practice there

1634-512: A speed of 4 mph (6.4 km/h), but Stevens abandoned propellers due to the inherent danger in using the high-pressure steam engines. His subsequent vessels were paddle-wheeled boats. By 1827, Czech inventor Josef Ressel had invented a screw propeller with multiple blades on a conical base. He tested it in February 1826 on a manually-driven ship and successfully used it on a steamboat in 1829. His 48-ton ship Civetta reached 6 knots. This

1720-445: Is a type of propeller design especially used for boat racing. Its leading edge is formed round, while the trailing edge is cut straight. It provides little bow lift, so that it can be used on boats that do not need much bow lift, for instance hydroplanes , that naturally have enough hydrodynamic bow lift. To compensate for the lack of bow lift, a hydrofoil may be installed on the lower unit. Hydrofoils reduce bow lift and help to get

1806-479: Is an opportunity to only change the pitch or the damaged blades. Being able to adjust pitch will allow for boaters to have better performance while in different altitudes, water sports, or cruising. Voith Schneider propellers use four untwisted straight blades turning around a vertical axis instead of helical blades and can provide thrust in any direction at any time, at the cost of higher mechanical complexity. A rim-driven thruster integrates an electric motor into

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1892-467: Is available as an option on most outboard motors. Although less efficient than an open propeller, they are particularly useful in applications where the ability to operate in very shallow water is important. They also eliminate the laceration dangers of an open propeller. Propane outboard motors are available from several manufacturers. These products have several advantages such as lower emissions, absence of ethanol-related issues, and no need for choke once

1978-484: Is considered unusual and exotic although some hobbyists continue to experiment. It is important to select a motor that is a good match for the hull in terms of power and shaft length. Whether using a displacement or planing vessel, one should select an appropriate power level; too much power is wasteful (adding unnecessary weight), and may often be dangerous. Boats built in the US have Coast Guard Rating Plates , which specify

2064-450: Is equipped with a manual piston release which will allow the operator to drop the motor down to its lowest setting. Large ships, boats and yachts will inevitably have inboard engines. Medium size vessels may have either inboards or outboards, and small vessels rarely have inboard motors. If one has a choice, these factors should be noted: Large outboards are affixed to the transom using clamps and are either tiller steered or controlled from

2150-437: Is generated at all. The condition continues until the prop slows enough for the air bubbles to rise to the surface. The primary causes of ventilation are: motor mounted too high, motor trimmed out excessively, damage to the antiventilation plate, damage to propeller, foreign object lodged in the diffuser ring. If the helmsman goes overboard, the boat may continue under power but uncontrolled, risking serious or fatal injuries to

2236-531: Is modelled as an infinitely thin disc, inducing a constant velocity along the axis of rotation and creating a flow around the propeller. A screw turning through a solid will have zero "slip"; but as a propeller screw operates in a fluid (either air or water), there will be some losses. The most efficient propellers are large-diameter, slow-turning screws, such as on large ships; the least efficient are small-diameter and fast-turning (such as on an outboard motor). Using Newton's laws of motion, one may usefully think of

2322-493: Is nearly always more than one so as to balance the forces involved. The origin of the screw propeller starts at least as early as Archimedes (c. 287 – c. 212 BC), who used a screw to lift water for irrigation and bailing boats, so famously that it became known as Archimedes' screw . It was probably an application of spiral movement in space (spirals were a special study of Archimedes) to a hollow segmented water-wheel used for irrigation by Egyptians for centuries. A flying toy,

2408-507: Is that if the impeller is run dry for a length of time (such as leaving the engine running when pulling the boat out of the water or in some cases tilting the engine out of the water while running), the impeller is likely to be ruined in the process. Air-cooled outboard engines are currently produced by some manufacturers. These tend to be small engines of less than 5 horsepower (3.7 kW). Outboard engines made by Briggs & Stratton are air-cooled. Outboards manufactured by Seven Marine use

2494-516: Is the angle of the motor in relation to the hull, as illustrated below. The ideal trim angle is the one in which the boat rides level, with most of the hull on the surface instead of plowing through the water. [REDACTED] [REDACTED] [REDACTED] If the motor is trimmed out too far, the bow will ride too high in the water. With too little trim, the bow rides too low. The optimal trim setting will vary depending on many factors including speed, hull design, weight and balance, and conditions on

2580-482: Is the tangential offset of the line of maximum thickness to a radius The propeller characteristics are commonly expressed as dimensionless ratios: Cavitation is the formation of vapor bubbles in water near a moving propeller blade in regions of very low pressure. It can occur if an attempt is made to transmit too much power through the screw, or if the propeller is operating at a very high speed. Cavitation can waste power, create vibration and wear, and cause damage to

2666-500: Is typically used: Electric outboard motors are self-contained propulsory units for boats , first invented in 1973 by Morton Ray of Ray Electric Outboards. These are not to be confused with trolling motors , which are not designed as a primary source of power. Most electric outboard motors have 0.5- to 4- kilowatt direct-current (DC) electric motors , operated at 12 to 60 volts DC. Recently developed outboard motors are powered with an alternating current (AC) or DC electric motor in

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2752-571: The Johnson Motor Company of South Bend, Indiana , Evinrude's company survived through acquisitions, eventually forming the Outboard Marine Corporation . His wife Bess died in 1933, at only 48 years old, and Ole Evinrude died the following year, 57 years old. They were both buried at Pinelawn Cemetery in Milwaukee, Wisconsin . After Evinrude died, his son, Ralph Evinrude , took over day-to-day management of

2838-492: The Paddington Canal from November 1836 to September 1837. By a fortuitous accident, the wooden propeller of two turns was damaged during a voyage in February 1837, and to Smith's surprise the broken propeller, which now consisted of only a single turn, doubled the boat's previous speed, from about four miles an hour to eight. Smith would subsequently file a revised patent in keeping with this accidental discovery. In

2924-456: The bamboo-copter , was enjoyed in China beginning around 320 AD. Later, Leonardo da Vinci adopted the screw principle to drive his theoretical helicopter, sketches of which involved a large canvas screw overhead. In 1661, Toogood and Hays proposed using screws for waterjet propulsion, though not as a propeller. Robert Hooke in 1681 designed a horizontal watermill which was remarkably similar to

3010-407: The transom is an important factor in achieving optimal performance. The motor should be as high as possible without ventilating or loss of water pressure. This minimizes the effect of hydrodynamic drag while underway, allowing for greater speed. Generally, the antiventilation plate should be about the same height as, or up to two inches higher than, the keel , with the motor in neutral trim. Trim

3096-417: The vapor pressure of the water, resulting in the formation of a vapor pocket. Under such conditions, the change in pressure between the downstream surface of the blade (the "pressure side") and the suction side is limited, and eventually reduced as the extent of cavitation is increased. When most of the blade surface is covered by cavitation, the pressure difference between the pressure side and suction side of

3182-414: The 1880s. The Wright brothers pioneered the twisted aerofoil shape of modern aircraft propellers. They realized an air propeller was similar to a wing. They verified this using wind tunnel experiments. They introduced a twist in their blades to keep the angle of attack constant. Their blades were only 5% less efficient than those used 100 years later. Understanding of low-speed propeller aerodynamics

3268-595: The Kirsten-Boeing vertical axis propeller designed almost two and a half centuries later in 1928; two years later Hooke modified the design to provide motive power for ships through water. In 1693 a Frenchman by the name of Du Quet invented a screw propeller which was tried in 1693 but later abandoned. In 1752, the Academie des Sciences in Paris granted Burnelli a prize for a design of a propeller-wheel. At about

3354-458: The Royal Navy's view that screw propellers would prove unsuitable for seagoing service, Smith determined to prove this assumption wrong. In September 1837, he took his small vessel (now fitted with an iron propeller of a single turn) to sea, steaming from Blackwall, London to Hythe, Kent , with stops at Ramsgate , Dover and Folkestone . On the way back to London on the 25th, Smith's craft

3440-695: The United States, is an oeconym from the Evenrud farm in Vestre Toten , where his mother was born. In October 1881, his father emigrated to America, followed the next year by Evinrude, his mother and two siblings. Three additional siblings were born in America. The family settled on a farm in Ripley Lake near Cambridge, Wisconsin . At age sixteen, Evinrude went to Madison , where he worked in machinery stores and studied engineering on his own. He became

3526-532: The absence of lengthwise twist made them less efficient than the Wright propellers. Even so, this may have been the first use of aluminium in the construction of an airscrew. In the nineteenth century, several theories concerning propellers were proposed. The momentum theory or disk actuator theory – a theory describing a mathematical model of an ideal propeller – was developed by W.J.M. Rankine (1865), A.G. Greenhill (1888) and R.E. Froude (1889). The propeller

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3612-516: The adoption of screw propulsion by the Royal Navy , in addition to her influence on commercial vessels. Trials with Smith's Archimedes led to a tug-of-war competition in 1845 between HMS  Rattler and HMS  Alecto with the screw-driven Rattler pulling the paddle steamer Alecto backward at 2.5 knots (4.6 km/h). The Archimedes also influenced the design of Isambard Kingdom Brunel 's SS  Great Britain in 1843, then

3698-419: The blade drops considerably, as does the thrust produced by the propeller. This condition is called "thrust breakdown". Operating the propeller under these conditions wastes energy, generates considerable noise, and as the vapor bubbles collapse it rapidly erodes the screw's surface due to localized shock waves against the blade surface. Tip vortex cavitation is caused by the extremely low pressures formed at

3784-400: The blades with a-circular rings. They are significantly quieter (particularly at audible frequencies) and more efficient than traditional propellers for both air and water applications. The design distributes vortices generated by the propeller across the entire shape, causing them to dissipate faster in the atmosphere. For smaller engines, such as outboards, where the propeller is exposed to

3870-426: The boat via clamps and thus easily moved from boat to boat. These motors typically use a manual start system , with throttle and gearshift controls mounted on the body of the motor, and a tiller for steering. The smallest of these weigh as little as 12 kilograms (26 lb), have integral fuel tanks, and provide sufficient power to move a small dinghy at around 8 knots (15 km/h; 9.2 mph) This type of motor

3956-400: The brass and moving parts on Turtle , was crafted by Issac Doolittle of New Haven. In 1785, Joseph Bramah of England proposed a propeller solution of a rod going through the underwater aft of a boat attached to a bladed propeller, though he never built it. In February 1800, Edward Shorter of London proposed using a similar propeller attached to a rod angled down temporarily deployed from

4042-453: The bushing in the hub is overcome and the rotating propeller slips on the shaft, preventing overloading of the engine's components. After such an event the rubber bushing may be damaged. If so, it may continue to transmit reduced power at low revolutions, but may provide no power, due to reduced friction, at high revolutions. Also, the rubber bushing may perish over time leading to its failure under loads below its designed failure load. Whether

4128-438: The cheap cast aluminum propellers on the often debris-prone inland waterways. Propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft ) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through

4214-600: The core of the tip vortex. The tip vortex is caused by fluid wrapping around the tip of the propeller; from the pressure side to the suction side. This video demonstrates tip vortex cavitation. Tip vortex cavitation typically occurs before suction side surface cavitation and is less damaging to the blade, since this type of cavitation doesn't collapse on the blade, but some distance downstream. Variable-pitch propellers may be either controllable ( controllable-pitch propellers ) or automatically feathering ( folding propellers ). Variable-pitch propellers have significant advantages over

4300-412: The deck above the waterline and thus requiring no water seal, and intended only to assist becalmed sailing vessels. He tested it on the transport ship Doncaster at Gibraltar and Malta, achieving a speed of 1.5 mph (2.4 km/h). In 1802, American lawyer and inventor John Stevens built a 25-foot (7.6 m) boat with a rotary steam engine coupled to a four-bladed propeller. The craft achieved

4386-441: The distinction of being the first submarine used in battle. Bushnell later described the propeller in an October 1787 letter to Thomas Jefferson : "An oar formed upon the principle of the screw was fixed in the forepart of the vessel its axis entered the vessel and being turned one way rowed the vessel forward but being turned the other way rowed it backward. It was made to be turned by the hand or foot." The brass propeller, like all

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4472-409: The engine at normal loads. The pin is designed to shear when the propeller is put under a load that could damage the engine. After the pin is sheared the engine is unable to provide propulsive power to the boat until a new shear pin is fitted. In larger and more modern engines, a rubber bushing transmits the torque of the drive shaft to the propeller's hub. Under a damaging load the friction of

4558-399: The filler is only subject to compressive forces it is able to do a good job. Often, the bushing can be drawn into place with nothing more complex than a couple of nuts, washers and a threaded rod. A more serious problem with this type of propeller is a "frozen-on" spline bushing, which makes propeller removal impossible. In such cases the propeller must be heated in order to deliberately destroy

4644-504: The first gasoline-powered outboard offered for sale in significant numbers. It was developed from 1903 in Grosse Ile, Michigan, with a patent application filed in 1905 Starting in 1906, the company went on to make thousands of his "Porto-Motor" units, claiming 25,000 sales by 1914. The inboard boat motor firm of Caille Motor Company of Detroit were instrumental in making the cylinder and engines. The most successful early outboard motor,

4730-552: The fixed-pitch variety, namely: An advanced type of propeller used on the American Los Angeles-class submarine as well as the German Type 212 submarine is called a skewback propeller . As in the scimitar blades used on some aircraft, the blade tips of a skewback propeller are swept back against the direction of rotation. In addition, the blades are tilted rearward along the longitudinal axis, giving

4816-498: The helm. Generally motors of 100 hp plus are linked to controls at the helm. These range from 2-, 3-, and 4-cylinder models generating 15 to 135 horsepower (11 to 101 kW) suitable for hulls up to 17 feet (5.2 m) in length to powerful V6 and V8 cylinder blocks rated up to 627 hp (468 kW)., with sufficient power to be used on boats of 37 feet (11 m) or longer. Small outboard motors, up to 15 horsepower (11 kW) or so, are easily portable. They are affixed to

4902-438: The helmsman and others in the water. A safety measure is a " kill cord " attached to the boat and helmsman, which cuts the motor if the helmsman falls overboard. The most common type of cooling used on outboards of all eras use a rubber impeller to pump water from below the waterline up into the engine. This design has remained the standard due mainly to the efficiency and simplicity of its design. One disadvantage to this system

4988-645: The late 1920s, such as the Roness and Sharland. In 1962 Homelite introduced a four-stroke outboard a 55-horsepower (41 kW) motor, based on the four-cylinder Crosley automobile engine. This outboard was called the Bearcat and was later purchased by Fischer-Pierce, the makers of Boston Whaler, for use in their boats because of their advantages over two-stroke engines. In 1964, Honda Motor Co. introduced its first four-stroke powerhead. In 1984, Yamaha introduced their first four-stroke outboards, which were only available in

5074-616: The low-power range. In 1990 Honda released 35 hp and 45 hp four-stroke models. They continued to lead in the development of four-stroke engines throughout the 1990s as US and European exhaust emissions regulations such as CARB ( California Air Resources Board ) led to the proliferation of four-stroke outboards. At first, North American manufacturers such as Mercury and OMC used engine technology from Japanese manufacturers such as Yamaha and Suzuki until they were able to develop their own four-stroke engine. The inherent advantages of four-stroke motors included: lower pollution (especially oil in

5160-477: The manufacturer, newer engines benefit from advanced technology such as multiple valves per cylinder, variable camshaft timing (Honda's VTEC), boosted low end torque (Honda's BLAST), 3-way cooling systems, and closed loop fuel injection. Mercury Verado four-strokes are unique in that they are supercharged . Mercury Marine, Mercury Racing, Tohatsu, Yamaha Marine, Nissan and Evinrude each developed computer-controlled direct-injected two-stroke engines. Each brand boasts

5246-401: The maximum recommended engine powers for the hulls. In the united kingdom, boats have CE plates on the transoms which specify maximum engine power, shaft length, maximum engine weight and maximum number of persons or maximum load. Outboard motor shaft lengths are standardized to fit 15-, 20- and 25-inch (38-, 51- and 64-centimeter) transoms . If the shaft is too long it will extend farther into

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5332-640: The meantime, Ericsson built a 45-foot (14 m) screw-propelled steamboat, Francis B. Ogden in 1837, and demonstrated his boat on the River Thames to senior members of the British Admiralty , including Surveyor of the Navy Sir William Symonds . In spite of the boat achieving a speed of 10 miles an hour, comparable with that of existing paddle steamers , Symonds and his entourage were unimpressed. The Admiralty maintained

5418-402: The outboard motor to be swiveled by the operator in almost all directions: Sideways for direction, up and down to change the thrust line according to speed or bow lift, elevate completely out of water for easy starting, placing the drive shaft and the propeller forward along the side of the boat for reverse, or put them inside the boat for propeller replacement, which can be a regular occurrence to

5504-462: The power head like a conventional petrol engine . With this setup, a motor can produce 10 kW output or more and is able to replace a petrol engine of 15 HP or more. The advantage of the induction or asynchronous motor is the power transfer to the rotor by means of electromagnetic induction . As these engines do not use permanent magnets , they require less maintenance and develop more torque at lower propeller speeds. Pump-jet propulsion

5590-447: The propeller an overall cup-shaped appearance. This design preserves thrust efficiency while reducing cavitation, and thus makes for a quiet, stealthy design. A small number of ships use propellers with winglets similar to those on some airplane wings, reducing tip vortices and improving efficiency. A modular propeller provides more control over the boat's performance. There is no need to change an entire propeller when there

5676-406: The propeller. It can occur in many ways on a propeller. The two most common types of propeller cavitation are suction side surface cavitation and tip vortex cavitation. Suction side surface cavitation forms when the propeller is operating at high rotational speeds or under heavy load (high blade lift coefficient ). The pressure on the upstream surface of the blade (the "suction side") can drop below

5762-403: The risk of collision with heavy objects, the propeller often includes a device that is designed to fail when overloaded; the device or the whole propeller is sacrificed so that the more expensive transmission and engine are not damaged. Typically in smaller (less than 10 hp or 7.5 kW) and older engines, a narrow shear pin through the drive shaft and propeller hub transmits the power of

5848-404: The rubber insert. Once the propeller is removed, the splined tube can be cut away with a grinder and a new spline bushing is then required. To prevent a recurrence of the problem, the splines can be coated with anti-seize anti-corrosion compound. In some modern propellers, a hard polymer insert called a drive sleeve replaces the rubber bushing. The splined or other non-circular cross section of

5934-545: The same time, the French mathematician Alexis-Jean-Pierre Paucton suggested a water propulsion system based on the Archimedean screw. In 1771, steam-engine inventor James Watt in a private letter suggested using "spiral oars" to propel boats, although he did not use them with his steam engines, or ever implement the idea. One of the first practical and applied uses of a propeller was on a submarine dubbed Turtle which

6020-599: The sleeve inserted between the shaft and propeller hub transmits the engine torque to the propeller, rather than friction. The polymer is weaker than the components of the propeller and engine so it fails before they do when the propeller is overloaded. This fails completely under excessive load, but can easily be replaced. Whereas the propeller on a large ship will be immersed in deep water and free of obstacles and flotsam , yachts , barges and river boats often suffer propeller fouling by debris such as weed, ropes, cables, nets and plastics. British narrowboats invariably have

6106-617: The system is pressurized. Lehr is regarded as the first manufacturer to have brought a propane-powered outboard motor to market by Popular Mechanics and other boating publications. The first known outboard motor was a small 11 pound (5 kg) electric unit designed around 1870 by Gustave Trouvé , and patented in May 1880 (Patent N° 136,560). Later about 25 petrol powered outboards may have been produced in 1896 by American Motors Co—but neither of these two pioneering efforts appear to have had much impact. The Waterman outboard engine appears to be

6192-500: The testing stage, and those that were proved unsatisfactory for one reason or another. In 1835, two inventors in Britain, John Ericsson and Francis Pettit Smith , began working separately on the problem. Smith was first to take out a screw propeller patent on 31 May, while Ericsson, a gifted Swedish engineer then working in Britain, filed his patent six weeks later. Smith quickly built a small model boat to test his invention, which

6278-455: The transverse projection of a blade and the developed outline of the blade. The blades are the foil section plates that develop thrust when the propeller is rotated The hub is the central part of the propeller, which connects the blades together and fixes the propeller to the shaft. This is called the boss in the UK. Rake is the angle of the blade to a radius perpendicular to the shaft. Skew

6364-466: The view that screw propulsion would be ineffective in ocean-going service, while Symonds himself believed that screw propelled ships could not be steered efficiently. Following this rejection, Ericsson built a second, larger screw-propelled boat, Robert F. Stockton , and had her sailed in 1839 to the United States, where he was soon to gain fame as the designer of the U.S. Navy 's first screw-propelled warship, USS  Princeton . Apparently aware of

6450-575: The water (wind and waves). Many large outboards are equipped with power trim , an electric motor on the mounting bracket, with a switch at the helm that enables the operator to adjust the trim angle on the fly. In this case, the motor should be trimmed fully in to start, and trimmed out (with an eye on the tachometer ) as the boat gains momentum, until it reaches the point just before ventilation begins or further trim adjustment results in an increase in engine speed with no increase in travel speed. Motors not equipped with power trim are manually adjustable using

6536-445: The water than necessary creating drag , which will impair performance and fuel economy. If the shaft is too short, the motor will be prone to ventilation. Even worse, if the water intake ports on the lower unit are not sufficiently submerged, engine overheating is likely, which can result in severe damage. Different outboard engine brands require different transom dimensions and sizes. This affects performance and trim. Motor height on

6622-401: The water), noise reduction, increased fuel economy, and increased torque at low engine speeds. Honda Marine Group , Mercury Marine , Mercury Racing, Nissan Marine, Suzuki Marine, Tohatsu Outboards, Yamaha Marine, and China Oshen-Hyfong marine have all developed new four-stroke engines. Some are carburetted, usually the smaller engines. The balance are electronically fuel-injected. Depending on

6708-675: The world's largest ship and the first screw-propelled steamship to cross the Atlantic Ocean in August 1845. HMS  Terror and HMS  Erebus were both heavily modified to become the first Royal Navy ships to have steam-powered engines and screw propellers. Both participated in Franklin's lost expedition , last seen in July 1845 near Baffin Bay . Screw propeller design stabilized in

6794-441: Was complete by the 1920s, although increased power and smaller diameters added design constraints. Alberto Santos Dumont , another early pioneer, applied the knowledge he gained from experiences with airships to make a propeller with a steel shaft and aluminium blades for his 14 bis biplane . Some of his designs used a bent aluminium sheet for blades, thus creating an airfoil shape. They were heavily undercambered , and this plus

6880-418: Was created by Norwegian-American inventor Ole Evinrude in 1909. Historically, a majority of outboards have been two-stroke powerheads fitted with a carburetor due to the design's inherent simplicity, reliability, low cost and light weight. Drawbacks include increased pollution, due to the high volume of unburned gasoline and oil in their exhaust, and louder noise. Four-stroke outboards have been sold since

6966-683: Was demonstrated first on a pond at his Hendon farm, and later at the Royal Adelaide Gallery of Practical Science in London , where it was seen by the Secretary of the Navy, Sir William Barrow. Having secured the patronage of a London banker named Wright, Smith then built a 30-foot (9.1 m), 6- horsepower (4.5 kW) canal boat of six tons burthen called Francis Smith , which was fitted with his wooden propeller and demonstrated on

7052-633: Was designed in New Haven, Connecticut , in 1775 by Yale student and inventor David Bushnell , with the help of clock maker, engraver, and brass foundryman Isaac Doolittle . Bushnell's brother Ezra Bushnell and ship's carpenter and clock maker Phineas Pratt constructed the hull in Saybrook, Connecticut . On the night of September 6, 1776, Sergeant Ezra Lee piloted Turtle in an attack on HMS  Eagle in New York Harbor . Turtle also has

7138-544: Was founded in Milwaukee. The simplest type of engine the company produced was a 2-stroke internal combustion engine that was powered by a mixture of gasoline and oil. Evinrude reported that his invention was inspired by rowing a boat on Okauchee Lake, a small lake outside Milwaukee, Wisconsin , on a hot day to get ice cream for his girlfriend, Bess. By 1912, the firm employed 300 workers. Evinrude let two motorcycle-mad teens tinker in his Milwaukee -based machine shop; one

7224-709: Was named Arthur Davidson , who went on to Harley-Davidson motorcycle fame, also based in Milwaukee . Ole Evinrude formed Evinrude Outboard Motors , which he sold in 1913 in order to look after his sick wife. In 1919, Evinrude invented a more efficient and lighter two-cylinder motor. Having sold his part in Clemick & Evinrude, he founded ELTO or the Elto Outboard Motor Company. (ELTO was an acronym for "Evinrude Light Twin Outboard".) Although Elto faced stiff competition from other companies, such as

7310-435: Was observed making headway in stormy seas by officers of the Royal Navy. This revived Admiralty's interest and Smith was encouraged to build a full size ship to more conclusively demonstrate the technology. SS  Archimedes was built in 1838 by Henry Wimshurst of London, as the world's first steamship to be driven by a screw propeller . The Archimedes had considerable influence on ship development, encouraging

7396-531: Was the first successful Archimedes screw-propelled ship. His experiments were banned by police after a steam engine accident. Ressel, a forestry inspector, held an Austro-Hungarian patent for his propeller. The screw propeller was an improvement over paddlewheels as it wasn't affected by ship motions or draft changes. John Patch , a mariner in Yarmouth, Nova Scotia developed a two-bladed, fan-shaped propeller in 1832 and publicly demonstrated it in 1833, propelling

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