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Tach on a 25hp Johnson

Old 11-04-2012, 07:06 PM
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Default Tach on a 25hp Johnson

I have some tachs laying around and would love to put one on my little motor, it's a 04 25hp Johnson tiller, but have know idea how to do it since it's a 2 cylinder not a 4 or 6, any guidance would be appreciated, thanks.
Old 11-05-2012, 04:26 PM
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somebody, anybody
Old 11-05-2012, 06:48 PM
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Circle, most that I know with little motors use a product called Tiny Tach as part of their rigging process since they're specifically designed for smaller motors. I've never used one but the place to find advice and rigging info is on another site that I visit regularly... Microskiff.com. They may even have a tutorial saved that you can refer to.
Old 11-06-2012, 06:26 PM
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Originally Posted by lemaymiami View Post
Circle, most that I know with little motors use a product called Tiny Tach as part of their rigging process since they're specifically designed for smaller motors. I've never used one but the place to find advice and rigging info is on another site that I visit regularly... Microskiff.com. They may even have a tutorial saved that you can refer to.
Thanks for the help, I will check that site out.
Old 11-07-2012, 04:00 AM
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Circle Hooked.
You can definitely put a regular tach on one of these motors.
There is table produced by Faria and one by Teleflex that lists all the major outboards and gives the number of poles on the engine's magneto. This then tells you what to set the tach to. Other than that you need to supply the guage with 12V power and then find the correct wire that carries that pulse and tap into it. I did it recently with a Johnson 15 HP which is also 2 cylinders.

The Faria list is here. (see last page) http://faria-instruments.com/site_ma..._W_OB_Tach.pdf

If you look at my boat build project. http://www.thehulltruth.com/boating-...oat-build.html

there is a picture in my 06-05-12 post showing the connection block. Unfortunately I do not show which one I actually connected to. I will look at the boat when I get home tonight and post the answer.
If you have any other questions please let me know.
Old 11-07-2012, 10:59 AM
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Originally Posted by trinaussie View Post
Circle Hooked.
You can definitely put a regular tach on one of these motors.
There is table produced by Faria and one by Teleflex that lists all the major outboards and gives the number of poles on the engine's magneto. This then tells you what to set the tach to. Other than that you need to supply the guage with 12V power and then find the correct wire that carries that pulse and tap into it. I did it recently with a Johnson 15 HP which is also 2 cylinders.

The Faria list is here. (see last page) http://faria-instruments.com/site_ma..._W_OB_Tach.pdf

If you look at my boat build project. http://www.thehulltruth.com/boating-...oat-build.html

there is a picture in my 06-05-12 post showing the connection block. Unfortunately I do not show which one I actually connected to. I will look at the boat when I get home tonight and post the answer.
If you have any other questions please let me know.
Thanks a ton, that's what I was looking for.
Old 11-07-2012, 11:10 AM
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There you go Scott! Told ya this place was good for something!












Old 11-07-2012, 12:30 PM
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Bob I have been finding that out
Old 11-07-2012, 05:39 PM
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Circle. Sorry, just got home and it is too dark to take photos.
I did find this wiring diagram for hooking up a tach to various 2 stroke engine manufacturers. This should be enough. You will see that on Johnson/Evinrude any one of three different wires will produce the pulse.

Name:  Tachometerhookup.jpg
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While I am at it I will upload two other useful wiring diagrams for small Johnson outboards.
15hp ignition circuit. (I am fairly sure the 25 hp will not be that different)

Name:  Johnson15HPElectricalDiagram.gif
Views: 11521
Size:  75.1 KB

And the basic Johnson throttle/kill/choke/starter circuit.

Name:  2011-07-23_132424_control_box_key-1.jpg
Views: 7849
Size:  93.7 KB

Happy tinkering!
Old 11-07-2012, 05:42 PM
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You are the best, thank very much.

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