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How do "Pulses per Revolution" relate to Tachometer Calibration for My Marine Engine?

When we talk about Pulses per revolution (PPR), or your tachometer's Pulse setting, we're talking about the electrical signal that our tachometers look for from your engine's ignition system.

Typically, a "Pulse" refers to an ignition firing, so another way to think of this is sometimes as Ignition Firings per revolution, though this is not always the case. For I/O Marine applications, 4, 6, and 8 cylinder applications are normally the same as automotive. Typically 4 Cylinder engines are 2 PPR, 6 Cylinder engines are 3 PPR, and 8 cylinder engines are 4 PPR.

Outboard applications are USUALLY 6 PPR. This signal comes from the alternator, which on multi-cylinder outboards is a 12 pole unit. In this case the Pulse Per Revolution is 1/2 the number of poles.

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