Johnson Tach Question

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Poppa003

Recruit
Joined
Aug 10, 2011
Messages
2
The Tach on my boat is stuck at 4500 rpm. I think all the wiring is good,the tach will
regester once the engine goes over 4500 rpms. My engine a 1991 70 hp.
My problem is, I was looking at boat tachs online and am confused by the
listing 4/6/10/12 pulse outboards and 12 pole outboards.
I have no idea what they are talking about. What is meant by pulse and pole?
 
H

Haffiman

Commander
Joined
Dec 17, 2009
Messages
2,454
Re: Johnson Tach Question

The outboard tach's are counting the AC frequency from the charging part of the alternator, normally same as number of coils and not the ignition pulses normally on a car or inboard.
For Evinrude/Johnson the normal setting is 6. On inboard engines and cars using an alternator with a 'W' outlet you may hook the tach there, but they are mostly using a 12 pole/pulse setting.
 
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