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  What tachometer "PULSE" ?

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Author Topic:   What tachometer "PULSE" ?
Jiles posted 10-04-2002 01:47 PM ET (US)   Profile for Jiles  
I have no experience with tachometers for small engines. I am looking at several tachometers on E-Bay and the sellers don't seem to know if the tac. they have will work with my motor. I have a 1985 Johnson 40 two cylinder. Can someone explain to me what the "pulse" setting is and what the tac. must be set on to work for my application? ---THANKS--
jimh posted 10-04-2002 08:51 PM ET (US)     Profile for jimh  Send Email to jimh     
Most tachometers used with outboards have calibration controls which are adjusted to match the pulse rate coming from the engine.

The pulses are generated by arrangement of coils and exciting magnets, and various numbers of pulses can be generated with each revolution of the crankshaft.

To make the tachometer read accurately, its calibration is adjusted to match the engine's pulses.

kingfish posted 10-04-2002 09:54 PM ET (US)     Profile for kingfish  Send Email to kingfish     
And Jiles,

It is a simple adjustment; if memory serves, you get a choice of settings for 4 cylinders, 6 cylinders or 8 cylinders.


jimh posted 10-04-2002 10:06 PM ET (US)     Profile for jimh  Send Email to jimh     
The pulse settings don't always correlate with number of cylinders. For example, a three cylinder Yamaha 70 is set to "6" pulses, while a three cylinder Yamaha 90 is set to "12" pulses.

Consult with the owner's manual for advice on which setting is appropriate.

Sal DiMercurio posted 10-04-2002 10:55 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
The correct tach setting, [ on the back of the tach ], for omc engines, is # 6.
The setting is on the back.
I'v found that sometimes other then omc tachs, on omc engines, don't match up.
I'v seen teleflex tachs that wont jive with an omc engine.
Your better off getting an omc tach for an omc engine, that way you know it's correct.
Try #6 & you should know as soon as you start it.
Dick posted 10-05-2002 04:28 PM ET (US)     Profile for Dick  Send Email to Dick     
The Teleflex book shows that the tach should be set at #5 for your 40 horse.
Bigshot posted 10-07-2002 10:23 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
An aftermarket tach such as Teleflex, Faria, VDO, and Gaffrig, etc. Will have a owners manual that gives engines and years and what settings. I believe Merc is the most simple and all are 12 pole. Yamaha is the most confusing and no matter what pole I put my tach on, my 30hp never read right.

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