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Checking RPM Gauge Accuracy on 32xx-gctid813619

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    Checking RPM Gauge Accuracy on 32xx-gctid813619

    Hi Group!

    We have the original square tach gauges (the small ones are square too) on our 1986 3270 with Hinos. Because of age, I wanted to confirm the RPM's shown on the dash gauge with a testing device.

    Is there a tester that can connect directly to the sender wires under the upper helm tach gauges? Or, are there any suggestions as to how going about confirming the RPM's shown on the dash gauge?

    Thanks for the suggestions.

    There are a number of stobe light tachometers that can be used -- even one in the Apple store -- not sure if it would work for engine RPMs.

    Alternative could be to use a device like a Noland RS11. You can connect it to the signal off the back of your Tachs (it does dual engines). It converts the analogue sender signal to Digital. Tach readings (along with a few other analogue gauge readings like temp, voltage, oil pressure) can then be read either off a NMEA 2000 device (like a chartplotter) or via their PC Application. I use the Noland on my twin Cummins engines and it's much more accurate than the analogue tachs and helps me get the engines to sync.


      An easy, and inexpensive way to determine accurate RPM's is with the use of a portable lasers tach like this:

      Typically, reflective tape is attached to a rotating part then strobed. If measuring at the fly wheel the indicated value is the actual value. If measuring the prop shaft speed you must then multiply the displayed value by the transmission gear box ratio.
      Jim Gandee
      1989 3888
      Hino 175's
      Fire Escape
      [email protected]
      Alamitos Bay, SoCal


        jim is correct, i got mine at harbor freight a few years ago. you put a small piece of refelective tape on any the harmonic balancer, or any shaft you want to test..very accurate, the one i got was approx $25 on sale