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Tach not working properly

kevinj

Advanced Contributor
"I have a 1979 Evinrude 140.

"I have a 1979 Evinrude 140. The tach is a Teleflex Vector model and worked just fine last year when I winterized the boat. I recently was able to get the boat out for the first time and the tach wasn't working properly. It reads about 1400RPM at idle and then quickly jumps to 4000 and then well past 6000 at only about 2/3 throttle. I know that I wasn't turning anything past 5500 when the tach last worked. Also the indicator needle does not stay steady but bounces around up and down while running at a constant throttle.

So, does this sound like a have a bad wire, is the tach itself bad, or do I have a rectifier that's starting to act up?

Thanks in advance for any help.

kevin"
 
Ck all your connections and th

Ck all your connections and then ck the rectifier to see if the charging system has a problem.
 
"Along with the connections et

"Along with the connections etc as Willard states above, check the back of the tachometer to make sure that the dial (if a dial exists) is set to number six (6)."
 
"I talked with my mechanic tod

"I talked with my mechanic today and he suggested the same possible problems. He had an extra tach lying around and gave that to me to use as a test to verify if the problem is my current tach or the rectifier. As I recall, I had the tach set on 6-pulse when I installed it. There shouldn't have been any reason to think that has changed, but I'll double check that to be sure.

One problem is the only tachometers he had were System Check tach's, so there is only an 8 pin plug on the back. We scoured several OMC shop manuals but none of them showed the pin-outs on these tachs. We did find a wiring diagram for the harness which showed the 12V, ground, and pulse wires beside each other. I connected two alligator clips to a 12V battery and started testing pins on the tach until I found the combination that zeroed the tach and illuminated the check lights. Our best guess, based on the wiring harness, is that the pulse line should be the pin next to the ground pin. I soldered wires to each of these pins and will use this as a test tach.

I need to get this problem solved ASAP as we are soon heading out for a week long boating vacation. I'll post back as soon as I get a chance to check the connections and use my test tach."
 
"I didn't need the test ta

"I didn't need the test tach afterall. I inspected my Teleflex tach and it was set on 6-pulse, as it should be. With the engine off I simply turned the pulse dial all the way down to 1, then back to 6 and ensured the arrow was squarely on the 6. I ran the boat this weekend and the tach worked just fine.

The problem could quite possibly be a wire or something else that just happend to situate itself properly between this past weekend and my prior outing. So, what I did with the pulse setting may have done nothing and the "fix" could have been a coincidence. Anyway, it's working for now.

KJ"
 
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