Author Topic: Tach issues  (Read 17210 times)

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Offline Rosscoe

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Tach issues
« on: June 15, 2015, 10:19:21 AM »
I recently reinstalled my Merc on the V163 after having it off for about 3 years. I got it running yesterday but now the tach is not working. I have not done anything under the dash so the wiring should be fine and I believe the wire(s) for the tach are part of the main harness, so if that's plugged in, it should work.
Do I need to have it running to trouble shoot and does anyone know what I should check? I have to have a working tach.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline thedeuceman

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Re: Tach issues
« Reply #1 on: June 15, 2015, 10:25:37 AM »
There should be a harness that plugs into your control, it has the tach wire and the trim gauge wire. Did you check and make sure that didn't get unplugged.
Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Rosscoe

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Re: Tach issues
« Reply #2 on: June 15, 2015, 10:33:15 AM »
No I haven't looked at the back of the control. Could be something there. I did fish some new wires for the bilge pump and also found some remnants of a mouse house.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline thedeuceman

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Re: Tach issues
« Reply #3 on: June 15, 2015, 10:37:48 AM »
You could check the resistance of the wire from the tack to the terminal strip on the motor, do you have a manual or a schematic?
I have a scanned version of the manual that's probably right for that motor
Joe
75 GT150 "SeaDeuced"... Its Back !!
92 16CSS "Attitude Adjustment" is for sale
75 CV-16V8, Project
74 CV-16... its Purple !

Offline Hyperacme

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Re: Tach issues
« Reply #4 on: June 15, 2015, 10:38:06 AM »
Merc install manual sent to your email Ross

Offline Rosscoe

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Re: Tach issues
« Reply #5 on: June 15, 2015, 10:43:22 AM »
Got it, thanks. Looks like what I have but I'll print it out and crawl under there today.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rosscoe

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Re: Tach issues
« Reply #6 on: June 15, 2015, 03:34:06 PM »
It appears that the "send" line from the tach has continuity all the way back to the motor. It appears to go to a rectifier. 12 volts at the gauge with the key on.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rich_V174SS

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  • 1967 V174 Crestflite SuperSport Modified
Re: Tach issues
« Reply #7 on: June 15, 2015, 05:24:19 PM »
Tach signal comes from the stator charge coil and the rectifier. If the rectifier is bad the tach will not work, also battery will not charge.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Rosscoe

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Re: Tach issues
« Reply #8 on: June 15, 2015, 06:14:29 PM »
How can I check the rectifer?
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rich_V174SS

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  • 1967 V174 Crestflite SuperSport Modified
Re: Tach issues
« Reply #9 on: June 15, 2015, 06:24:00 PM »
It can be checked with an ohm meter that has a diode checker, or you can just check battery voltage with a volt meter when it's running to see if it's charging.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Rosscoe

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Re: Tach issues
« Reply #10 on: June 15, 2015, 06:38:05 PM »
My meter has a doide checker. The rectifier has 3 terminals. Which one and what am I looking for?
Thanks Rich
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rosscoe

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Re: Tach issues
« Reply #11 on: June 15, 2015, 06:39:21 PM »
And do I check it with the key on?
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rosscoe

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Re: Tach issues
« Reply #12 on: June 15, 2015, 06:46:23 PM »
Battery 12.9 running 13.2
Thats not enough is it?
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rich_V174SS

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  • 1967 V174 Crestflite SuperSport Modified
Re: Tach issues
« Reply #13 on: June 15, 2015, 07:01:44 PM »
The rectifier actually has 4 terminals, the 4th being the metal plate that grounds it to the engine and negative battery. I think if you use the diode checker from each yellow terminal to ground you'll get a reading in one direction but not the other, same between yellow and red terminal. Something like that, it's been a while since I've done it.

If you have a higher voltage with the engine running then it should be charging, especially if you rev the engine higher.
« Last Edit: June 15, 2015, 07:54:26 PM by Rich_V174SS »
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Rosscoe

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Re: Tach issues
« Reply #14 on: June 15, 2015, 07:53:19 PM »
I'll post my meter readings when I get puter. Maybe the tach is just bad? Rather odd in anycas since everything was fine when I parked it. So much for ol reliable.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rosscoe

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Re: Tach issues
« Reply #15 on: June 15, 2015, 08:48:23 PM »
Meter on diode check and alternating probes.

Yellow to grd .556
flip
2.002
2nd Yel to grd .556
flip
2.002

Red to grd, either way, .OL

Is there such a thing as a rectifier on its way out?
Not sure how to test the tach beyond what I have done.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Rich_V174SS

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  • 1967 V174 Crestflite SuperSport Modified
Re: Tach issues
« Reply #16 on: June 15, 2015, 08:51:57 PM »
Have another tach to test it with, maybe something from another boat? Doesn't necessarily need to be accurate, just to test that the needle moves with rpm.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115

Offline Rosscoe

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Re: Tach issues
« Reply #17 on: June 15, 2015, 09:35:07 PM »
I do have a J/E tach.
I have an automotive tach and dwell meter too but not sure how to connect that to an outboard, or if its even possible.
Ross
61 Surflite 1964 90HP Johnson project
67 V163 Bayflite Super Sport  1989 100HP Merc
67 V164 Bayflite 120HP
67 V174 Crestflite Rat Rod
71 V175 Crestflite 350ci -Jet
73 GT 160
84 CVX 17  83 115 Merc
88 CVX-23 350 Mag

Offline Plugcheck

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Re: Tach issues
« Reply #18 on: June 15, 2015, 09:38:40 PM »
Not sure I can add anything here since my work on outboards is thin.  Diodes have a forward conduction voltage typically in the .55 to .7 voltage range, but the reverse should be nearly infinate.  Your meter on diode range is a bit more sophisticated than an ohmeter by applying bias to the pn junction.  If I knew the configuration on the rectifier, schematic, I could tell ya what readings you should expect.  I suspect the tach is powered on the rectifier side, but the tach signal is the ac pulse coming directly from the stator coil.  Hope this helps, Michael.
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Rich_V174SS

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Re: Tach issues
« Reply #19 on: June 15, 2015, 09:53:10 PM »
Correct, tach signal comes directly off the un-rectified leg of the stator to sense pulses. To properly test the rectifier it needs to be disconnected from the stator and battery or else your meter will read them as part of the circuit.
1967 V174 Crestflite SuperSport Modified
1987 Mercruiser 190 3.7LX/Alpha One

1970 V176 Swinger
1983 Mercury 115