1977 Johnson 140 O/B No Tach

[flyboy53]

Here is a little history with my problem...Origionally,I had no ignition so when I did the troubleshooting I changed the powerpack. While I was at it, the coils were origional and all cracked, so I replaced them too. When I took it out for a test run, everything ran great. After 10 minutes I looked down and had lost the tach and was not charging the battery. I ohmed out the rectifier and it checked good, but went ahead and replaced it anyway. I now am charging but still no tach. After verifying the wiring from the motor to the tach, I felt sure the tach indicator was bad. NOT! After installing the new guage, still nothing....Again, the motor runs great! Charges! Just no Tach. Any ideas out there? Is the tach signal the same pulse as the charge system? I appreciate your help in advance.....

 

[Joe Reeves]

Re: 1977 Johnson 140 O/B No Tach

Tach should be set to #6 (6 pulses).

Is the charging system now working as it should..... charging battery? If so, the stator battery charging coils and the rectifier must be okay, however, double check that rectifier as follows.

(Small Rectifier Test)
(J. Reeves)

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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If all checks out okay, possibly a break exists in one of the tach circuit wires.

As an after thought and with no intentions of insulting your intelligence, is there any possibility that the battery is hooked up backwards or has been charged backwards?

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

Thanks Joe for the quick response! The battery is hooked up correctly (no insult taken!) I will check the rectifier again per your instructions. The pulse is set at 6 on the guage. I have rung out the wiring from the engine to the guage and made sure there is also 12v to the guage as well....The only other thing I am concerned about is if it could be the stator or the pick-up inside the stator. Looks like to pick-ups there and one appears to be farther from the stator than the other one....Since it runs perfect, is there a seperate pulse signal for the guage? Thanks...

 

[Joe Reeves]

Re: 1977 Johnson 140 O/B No Tach

The tachometer operates off of the charging system via the yellow/gray or yellow (if no yellow/gray exists) wire of the rectifier. If the charging system is functioning and the rectifier is okay..... that is all that's needed to operate the tachometer.

This hold true if: The tach is good, No break exists in the gray wire, 12v is supplied to the tach, Tach is set to #6, Tach ground is good.

 

[bkwapisz]

Re: 1977 Johnson 140 O/B No Tach

I just had a similar problem and the issue was bad connectors at the remote box where the tach harness came out. There was a rubber connector that didn't have a good connection and I could find no real way to repair ir so I bypassed it (12V, tach signal and Ground) and all is well. Good thing I bought a plug-n-play harness for $70. Guess that's what happens with old boats though.

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

I pulled the flywheel off today to gain access to the stator. It looks ok, however there are a few areas where the flywheel has touched the stator. I removed the stator and checked the wiring for breaks. All is good there. I did ohm out the wiring as follows: Yellow to Yellow/Grey wire ohms out at 1.2 ohm. Same reading when I go from wire to stator case. The Brown to Brown/Yellow wiring going to the powerpack reads 650 ohms. I am wondering if the powerpack even though it is new, could be the problem? My next project is to hook up another tach directly to the yellow wire coming off the stator and see if it reads anything.....Anybody have another suggestion?
Thanks!

 

[ezeke]

Re: 1977 Johnson 140 O/B No Tach

The rectifier should already be connected to the yellow wires from the stator and therefore connected to the gray tachometer signal wire. What is the AC voltage reading on your gray wire at the gauge at fast idle?

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

I have not checked the AC voltage there. Tell me how to connect the AC voltmeter. Grey to Ground? Is this ok? I am afraid of smoking the rectifier.

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

The AC voltage is about 1.2v with the engine running at approx 1500rpm.
I checked the resistance of the stator yellow & yellow/grey wires and got this reading: Yellow to Grd= .8 ohm Yellow/Grey to Grnd .9 ohms
Each wire to grnd .3 ohms. I would think that the yellow wires should be open to ground.....A new stator is pricey just to change it without knowing for sure....

 

[bkwapisz]

Re: 1977 Johnson 140 O/B No Tach

I'm pretty sure that AC voltage is WAY low. IIRC it's supposed to be about 25V or so, but I haven't checked in a long while. There are some threads on here which outline the testing procedure and give the proper values though...


EDIT** Read the thread in the link below. It's explained very well several times as well as Regulator/Rectifier testing. I actually printed this thread and took it out to my boat to determine what's wrong:

http://forums.iboats.com/showthread.php?t=411196

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

Thanks for the link....I disconnected both yellow wires from the stator and checked for ACV and it was about 30v at idle. So I figured the stator was ok. After scratching my head for a bit, I decided to reverse the two wires (yellow and yellow/gray) and hook everything back up and give it a try. (why not? AC voltage is the same no matter which way they are connected) And guess what? The tach started working...And I am still charging the battery...The only real change that took place is that the I connected the tach (gray) wire to the other (yellow) wire directly from the stator. Not sure how this changed anything but it worked....Thanks to all who posted on here to help out.

 

[ezeke]

Re: 1977 Johnson 140 O/B No Tach

That usually indicates that the diode(s) on one side of the rectifier is/are bad. That indicates that the rectifier should be replaced.

 

[flyboy53]

Re: 1977 Johnson 140 O/B No Tach

I agree however the motor is still charging the battery. I figured when I reversed the yellow leads from the stator and the tach started working the charging circuit would not work. I have ohmed out the rectifier and it checks good....In my real life I am a pilot and aircraft mechanic. We call them gremlins. Thanks Again!

 

[nphilbro]

Re: 1977 Johnson 140 O/B No Tach

I understand this is an old thread so but I'm posting a follow-up for others finding it in a search for this same problem and want to confirm that moving the sender lead from gray/yellow-gray bridge to the adjacent isolated yellow lead terminal (which was position 1 on the motor terminal block) solved this problem for me too on my 1980 140hp V4 Johnson.

I'm on my 3rd tach in the 2 months since buying this motor. In all instances they would zero out with a key turn indicating power and a connection but would not register a pulse.

I logged countless wasted hours troubleshooting when I should have been fishing trying to find my error in a 100% to spec installation. I'd already mounted all my accessories to the dash (since I find control box electrical connections temperamental and prone to enigmatic failure) using segregated fused circuit banks with redundant power and ground to the batteries so I knew I was getting desperate when I reconnected the Johnson Remote power/ground/send terminals directly into the accessory plug below the key. Exact same result.

After duplicating flyboy's fix my tach now works and I'll test the charging in the morning.