<Tr> <Td> LEHR - 2.5 HP </Td> <Td> 14 ° </Td> <Td> </Td> <Td> </Td> </Tr> <P> Motor height on 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 . </P> <P> Trim 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 . 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 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 RPM increase with no increase in speed . Motors not equipped with power trim are manually adjustable using a pin called a topper tilt lock . </P> <P> 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 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 . </P>

What is power trim on a boat motor
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