OMC Tach Settings

I am interested in Johnson outboard tachs and how they work. I understand that the tach receives the signal from the tach pulse that is generated by the stator as the flywheel turns. Could you explain this in more detail? How many pulses are usually generated in one revolution of the flywheel? The reason I ask is this. Most OMC tachs have an adjustable setting on the back, 4P, 5P, 6P etc., however I have been told that ALL Johnson outboards should be always set on 6P since they all emit 6 pulses per revolution. That doesn’t make sense to me. Why would there be different settings on the tach if they all were to be set on 6? I thought that it has to do with the number or poles on the stator. For a 12 pole stator it would be set on 6, for a 10 pole stator it would be set on 5, and for a 8 pole stator set it on 4.Would that be correct, or should they all be set on 6? I am only interested in OMC engines since that is what I own. Any input you have would be greatly appreciated. Again, I hope you can answer this question. Thanks


You are correct on the settings vs. poles in the stator. It is just most OMC engines in the last 20 years have 12 pole alternators (Stator). The tachs are manufactured by an instrument company and use that manufacturers "universal" components in an OMC approved casing.




Please submit whatever questions you have to  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Mark C.


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