Cubic Centimeters (cc) - A unit of measurement for the displacement of the engine, which helps identify its relative size.
GPM - A unit of measure for water flow, same as “gallons per minute.”
Head - A term used to describe pressure.
Impeller - The moving part of the pump that is connected to the engine. As this spins the water goes into the center of the impeller and goes into the vanes. It is then forced to the outside of the impeller by centrifugal force as the impeller spins.
Mechanical Seal - Keeps the water inside the pump. It is a two-piece seal. One piece is moving with the impeller the other piece is stationery and surrounds the shaft. The two pieces are pushed together and create a seal so the water can’t get out.
OHV - Same as “overhead valve”, an improved way to control exhaust and intake valves on internal combustion engines.
PSI - A unit of pressure, same as “pounds per square inch”.
RPM - Same as “revolutions per minute.” The amount of revolutions (turns) an engine makes in one minute.
Self-Priming - The ability of a pump to create a partial vacuum by purging air from the intake hose and pump casing. Requires water to be added to the pump casing to start the priming process.
Shim adjustment - There are small metal washers between the shaft and the impeller. These move the impeller closer to the volute to optimize the efficiency in the pump. This gap is usually 0.6-1 mm.
Side Valve - A type of internal combustion engine that uses a conventional “L” type cylinder head with the exhaust and intake valves on the side of the engine.
Suction Head - Is the vertical distance from the top of the water to the suction of the pump (eye of the impeller to be exact).
Torque - A unit of measurement of the immediate twisting force required to turn the pump. Measures the rational force that pumps the water. Measured in ft-lbs. Per SAE J1940 standards.
Total Head - Is the vertical height from the top of the water to the discharge of the pump.
Priming - The pump body must be filled with water before running the pump. The pumps are called self-priming because it does not need the suction hose to be filled with water before using - the pump will evacuate the air form the suction hose. The eye of the impeller always needs to be under water or the pump will not work, therefore the pump body needs to be filled with water before starting the pump.
WP - Same as “water pump.”