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Closet Powerboater
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I have 2 steering stations on my boat, but only one analog tachometer at the lower station.

I understand that analog tachometers are notoriouly unreliable, and mine said, at survey, that I was 1000rpm short of max at WOT. I may be over-pitched, but would like to verify that it's not the tach reading incorrectly.

My solutoin to both problems, is hopefully to get a good quality (read: accurate) tach that I can add to the upper statation. Then I can have the reading I need, and double check the accuracy of the lower one.

Suggesitons on which one to get? I'm not sure how they work to be honest... I understand the analog ones run of the alternator, but others don't. This one clips to the fuel line, so I really have no idea how it works.

MedSailor
 

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simplisticly some event that happens every time the engine rotates generates
a small signal(spark). a digital counts the events where an analog dumps them into a capacitor and measures the voltage. The details of how this is done can get rather involved,
and unless you are designing one not important. The pickup can be distributor spark, a magnet on the flywheel, or even a spot of paint on the crank pulley. I have always liked the magnet on the flywheel more difficult to install but permanate.
 

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Living the dream
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350 Posts
The original alternator driven tacho/hourmeter on my boat never worked properly. Replaced it with a not inexpensive alternator driven digital tachometer/hourmeter with analogue display and it doesn't work properly either. Not sure if faulty or if there's something wrong with my alternator. I have contemplated the idea of a second tacho at the helm too, because the engine control is in the cabin and my thoughts now are if I do this to definitely use a magnetic / optical pickup variant to eliminate problems that may be caused by the alternator. I did purchase a cheap non contact tachometer off Ebay and use it to calibrate, or rather attempt to calibrate, the new tachometer. At the moment I set engine revs by sound and throttle position, but the tool remains on the boat allowing me to do spot checks if needed.
 

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The Tiny Tach uses a piezoelectric crystal sensor that detects the vibration of the diesel injector pipe and turns it into an electrical pulse. They work well. The display is small, but that might be an advantage depending upon the location.

Design Technology, Inc., Home of Tiny-Tach

As for me, I'm going to add on to my NMEA2K network with an Actisense Engine Monitoring Unit.

EMU-1: Engine Monitoring Unit

All of the info from the engine will be on all of my displays.
 
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