Definition of Engine Hour Meterby Steve Wager
Most people may never encounter an engine hour meter, but you'll find hour meters employed in applications ranging from airplanes to generators. Engine hour meters are used for warranty and maintenance scheduling in both combustion and electric motors that do not effectively track use in miles. Engine hour meters come in a variety of forms, and are able to track usage time in a couple of different ways.
One of the most common applications for an engine hour meter is in aviation. Airplanes need strict maintenance based on run time, and hour meters effectively fill that need. One of the earliest hour meters is the Hobbs meter, and it's still available today. They are so common that hour meters will sometimes be referred to as a Hobbs meter.
Another common place to find hour meters is in medium and large sized boats. Just like planes, marine engines need regular maintenance to prevent premature wear and system failure. Medium and large boats may have two or more motors for propulsion, but they will often run on a single motor to save on fuel. Other systems in boats from the generators to the bow thruster may have hour meters to help give an owner a complete picture of system status with regard to maintenance.
Digital and Analog Hour Meters
Hour meters are available in analog and digital styles. Analog meters function much like a simplified watch, and they are very reliable and easy to read. Analog meters are commonly made in brass to help deal with extreme operating environments. Digital meters are also available, and can be a cost-saving alternative. Digital hour meters will sometimes be bundled with other engine information systems like a tachometer.
Measuring Actual Run Time
Most hour meter installations will have the counter activated whenever the ignition is set to on. Since the ignition can be on without the engine running to power accessories or while servicing, this type of installation will sometimes give a false count of actual engine run time. A modern alternative counts engine revolution via a sensor, and only logs time if the engine is actually running.
When Hour Meters Lie
Just like a car's odometer, an hour meter cannot be spun backward, but they can be replaced. Always be sure you are getting the whole picture when evaluating used equipment by inspecting all systems for signs of wear that might be more extensive than typical of what the hour meter is reading. Service records should match the hour meter reading as well. It's always best to consult with a professional before relying on an hour meter when making large equipment purchases.
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