Tach only works until about 2500 rpm

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crb478

Lieutenant Junior Grade
Joined
Dec 6, 2006
Messages
1,036
I took my boat out yesterday and the tach would only work up to about 2500 rpm. Above that it would go to 0 until you throttled back and then it would work again starting about 2500 rpm down to about 750 at idle. Any ideas if this is a bad tach or if the rectifier or timing base might be causing this? The motor is an 1975 Johnson 115. The motor starts easily and runs good. The tach issue just started and I don't want to start replacing parts or mess anything up until I know what is wrong. Any ideas?
 
AEROCOOK

AEROCOOK

Master Chief Petty Officer
Joined
Jul 28, 2004
Messages
872
Re: Tach only works until about 2500 rpm

My 1988 110 did the same thing. It turned out to be the rectifier. There are posts in the forum that should tell you how to test the rectifier with an ohm meter.
 
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crb478

Lieutenant Junior Grade
Joined
Dec 6, 2006
Messages
1,036
Re: Tach only works until about 2500 rpm

Thanks, I have my manual at home, but wanted somewhere to start without tearing things apart too much.
 
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crb478

Lieutenant Junior Grade
Joined
Dec 6, 2006
Messages
1,036
Re: Tach only works until about 2500 rpm

Took the cover off and found that one of the rectifer wire had broken. Ordered a new one here from I-boats so I should be good to go in a few days.
 
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