Poles, pulses and Tachometer

J

Jeb1971

Petty Officer 3rd Class
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Mar 26, 2007
Messages
85
I am having trouble determining which tach to get for an '85 Evinrude 235HP.

Are poles the same as pulses?
how many poles does the 235 have?

Can you use an automotive tachometer on this motor?

Thanks, John
 
W

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: Poles, pulses and Tachometer

6p is the typical setting and no, you can't use an auto tach.
 
J

Jeb1971

Petty Officer 3rd Class
Joined
Mar 26, 2007
Messages
85
Re: Poles, pulses and Tachometer

Thanks fellas, for the advice and information!!
John
 
HighTrim

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Poles, pulses and Tachometer

To try and explain it simply, tachometers read off the alternating pulses from the stator. Any of the leads from the stator charging portion can be used for the signal. The designated tach signal wire is merely attached to one of those. Tachs have rotary switches on the back that set it to different numbers of coils in the charging circuit, times two because there is a positive and negative pulse for each coil for each cycle. Tachs measure pulses. That being said, you need a tach that has the setting that you need designated on the rotary switch.
 
J

Jeb1971

Petty Officer 3rd Class
Joined
Mar 26, 2007
Messages
85
Re: Poles, pulses and Tachometer

Thanks Hightrim.

I understand what you're saying. When I was running the motor, I did set the tach switch for 6 pulses, but it still stayed at about 1000 rpm's even when I revved it up.

I guess my tach has probably reached its life span and gone bad, but it seemed to work well when I used it with my old 125 evinrude (I think that was set at 4 pulses)..

Too bad for me because the face of the tach matched the faces of my other instruments.

Ill look on ebay, or maby overtons for a tach that has a 6 pules capability.

Thanks for explaining the issue.

\John
 
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