testing rectifier on evinrude 75 1978

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branson

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May 29, 2011
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7
I have read many posts here for charging problems and testing rectifiers and beaucause mechanics here [Greece] are for the bottom of a lake here is my problem.With an ommeter and the black lead on ground no readings reverse the leads and i have readings [480om] on two yellow wires but not the red wire.Now with black lead on red wire no readings reverse no readings olso.With motor on idle and multimeter on DCV i have 11.5volts on red wire.Is my rectifier dead for sure?
thanks in advance and a big hey to all of you here
 
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Will Bark

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Aug 1, 2010
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1,470
Re: testing rectifier on evinrude 75 1978

If I want to see if my engine is charging all I do is take a reading with my meter of the voltage at the battery with the engine off; then I crank the engine and take a reading and see if the voltage is higher than before. If it is then I know that it is charging the battery; voltage should gradually increase as the engine runs; mine charges slow but it will be above 12.5 volts as I start the reading. No increase then start looking elsewhere.
 
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branson

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May 29, 2011
Messages
7
Re: testing rectifier on evinrude 75 1978

thanks for your replay Will Bark i test it today and i read 12.2v with engine off and same with engine on 3000rpm.I allready order a new rectifier.
 
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wilde1j

Vice Admiral
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Apr 15, 2002
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5,964
Re: testing rectifier on evinrude 75 1978

You can also check the stator by measuring the AC voltage (@ fast idle 1200RPM) across the yellows to the rectifier. Sould get 30 VAC or more.
 
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branson

Cadet
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May 29, 2011
Messages
7
Re: testing rectifier on evinrude 75 1978

I test it first stator is fine.On evinrude 1978 75hp stator 12 poles it is normal charge 12.2 volts on 3000rpm?
 
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boobie

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Nov 5, 2009
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20,826
Re: testing rectifier on evinrude 75 1978

wilde1, where did you get the 30 volt spec and what meter are you using??
 
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