Minnesota Classic Glastron Forum
General Category => General Discussion => Topic started by: Rosscoe on June 15, 2015, 10:19:21 AM
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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.
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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.
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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.
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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
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Merc install manual sent to your email Ross
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Got it, thanks. Looks like what I have but I'll print it out and crawl under there today.
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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.
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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.
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How can I check the rectifer?
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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.
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My meter has a doide checker. The rectifier has 3 terminals. Which one and what am I looking for?
Thanks Rich
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And do I check it with the key on?
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Battery 12.9 running 13.2
Thats not enough is it?
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Makes sense it should be removed from the circuit to be tested for accurate results, BUT if it is charging the battery, doesn't that say something?
I would think there would be a way to check for the pulse/signal at the tach to see if its even getting one? I have proved the wire is unbroken.
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I'll check to see how mine's hooked up.
Give me a few minutes ...
Could we disconnect my tach lead from control box, and jumper it to your tach ?
Just to make sure that's the problem ?
I'm kind of busy this weekend ... but have next week off.
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I'll check to see how mine's hooked up.
Give me a few minutes ...
Could we disconnect my tach lead from control box, and jumper it to your tach ?
Just to make sure that's the problem ?
I'm kind of busy this weekend ... but have next week off.
Maybe
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On wiring harness in engine, there are 4 wires.
Tan - not connected.
Brown / White - connects to a Brown / White and run up to control box.
Light Green / White - connects to an Aqua Green / White.
Light Blue / White - connects to a White.
The Aqua green and White run up to what look like mini solenoids with wires running down to the starter solenoid.
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Mine looks pretty much the same. Tan is not connected. A couple of them are for the trim up and trim down solenoids.
I don't believe there is a wiring problem there. Its just the main harness and a couple of bullet connectors.
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It has got to be either the tach or the rectifier. Leaning towards the rectifier but the battery IS charging. Part is in the 45.00 range from what I am seeing. I hate just throwing parts in there though.
I did blow a fuse when wiring the bilge switch. I wonder if that could have taken out the rectifier?
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" A couple of them are for the trim up and trim down solenoids."
OK .. that what those are ...
Let me know if you want to try my boats tach leads.
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OK
Think I'll try my J/E tach and see what that does. There has GOT to be a way to check for a signal/pulse at the tach. I'm looking all over the internet.
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your merc has a grey wire at the voltage regulator with engine running look for an A/C voltage reading if present check at tach grey wire and hopefully you will get same result,if so check for power and ground at tach as well should be battery voltage if all readings are ok than replace tach. As far as ACARR83 ,I think your tach signal is green so check for A/C power there at tach and power on yellow and ground
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Anyone have an idea as to where 12v should go on this old J/E tach I have? Nothing is marked. Maybe either terminal? Not sure why they'd put 2 unless for jumpering purposes. I just dont want to fry something if I havent already done so.
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Ross
I am not sure but maybe the different connecting points on the tach could be for different number of cylinder numbers. Save you have 2 ,4, 6 cylinder motor.
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i think i have one like that in my box of gauges.
i think it gets power and pulses from the grey wire, screw terminals select the number of pulses per rev (number of poles on the sataor).
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Never seen one quite like that, must really be an oldie.
On mine purple is 12V+, black is ground, and grey is the signal from the stator.
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Yo Ross. Try the 'Marine Engine' or 'Iboats' Merc forum(s). Couple'a the guys over there really know their chit.
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Ross
I am not sure but maybe the different connecting points on the tach could be for different number of cylinder numbers. Save you have 2 ,4, 6 cylinder motor.
Thats probably what the extra terminal is for. I think this thing is from the 60's so one of them is probably for a 2 banger and the other a 4 BUT as you can see, there are two wires on it (just as I received it) so I am guessing the two that are on there are a trigger/send and a ground, so only one of the other can be for 12v
I cant believe there are no markings.
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Like Joe and Doug said, I had assumed the gray was the signal wire. Maybe the one next to it is the difference between 2 and cylinder and that leaves the one next to the ground for 12v?
Kinda turning into a hassle just to find out of my tach is bad.
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your merc has a grey wire at the voltage regulator with engine running look for an A/C voltage reading if present check at tach grey wire and hopefully you will get same result,if so check for power and ground at tach as well should be battery voltage if all readings are ok than replace tach. As far as ACARR83 ,I think your tach signal is green so check for A/C power there at tach and power on yellow and ground
Guess I should try this.
I should also look at my own pictures. Two terminals are already tied. I'll see if I can find any kind of model number on it and do some research.
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Yo Ross. Try the 'Marine Engine' or 'Iboats' Merc forum(s). Couple'a the guys over there really know their chit.
I'll check them out. Thanks
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Fwiw you probly won't 'smoke' the tach if'n the pulse setting/jumper is wrong. It just won't read right.
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That's cool as long as I don't smoke the rectifier! (if it isn't already toasted)
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That's cool as long as I don't smoke the rectifier! (if it isn't already toasted)
Sounds like yers is workin. Long's it's 13v or so at idle you're good. As rpm's increase it should climb a lil, but not a whole lot.
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So it appears I can rule out the rectifier.
Guess I'll order a new tach.
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if you want i can look ans see if i got something tonight
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if you want i can look ans see if i got something tonight
That would be great...or if I can figure how to connect the one I have. I might mess with it today or go work. Depends on the weather.
Thanks Joe
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Yo Ross. Might be worth asking over on the antique outboard forum about correct wiring for that tach?
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I haven't been on many other forums.
In any case, I think this one may be bad too. I connected the obvious ones (gray, black) and connected 12v to one of the open terminals and started the motor. Tach went to 3k so I thought I would try the other one and it read the same thing. I noticed after I shut the motor off it was still sitting at 3k. Banged on it some and it went to 4k. Its stuck up in that area.
I also verified once again that the battery is charging. Went up into the 14v range when revved. I removed my old tach and banged on that and couldn't get the needle to move at all. May be it didnt like the winter I left it outside, or it didn't like my humid barn. Hope that trend does not continue because if that is the case, I've got the whole herd in the barn possibly doing more harm than good?
I'm ordering a new tach. This one was installed when the guy I bought the motor from rigged the boat. Its about 10-11 years old. Faria brand.
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Not sure about Mercs, but on a OMC when you key the ignition "on". The tach should zero.
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Yeah that sounds like what I have been reading. It was at zero before I turned the key on. It went to 3k, stayed there, key on or off.
I was hoping to use this one in the 61 with the Evinrude, but that's a ways off. I'll hang on to it just in case.
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If the tach has an adjustment screw on the back for setting the number of poles or cylinders sometimes the contacts inside get mucked up. I take a screw driver and rotate the screw back and forth quickly a number of times to improve the contact, then set it to the required position.
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Argh
2 seconds late. I just ordered one. Oh well, I'd still like to know if the old one is good and will try that. I have enough boats, I am sure I can use it. Speaking of that, since I never had any instructions, how does one determine that setting? Number of poles?
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I bleve the "P" stands for 'pulses'. Not 'poles'.
12 pole = 6 pulses.
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So my current tach is set at 5. Not sure of the correlation there with a 4 cylinder.
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If the tach is used with an I/O engine you'd set it to corresponding cylinders like 4, 6, or 8. When used with an outboard it's usually 12 pole alternator.
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So my current tach is set at 5.
Should be set at 6. There's no correlation to number of cylinders.
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Some tachs have numbered settings like 1 thru 4 or 5 and a small tag indicating what each number corresponds to. As an example (but not necessarily an accurate depiction) 1=4 cyl, 2=6 cyl, 3=8 cyl, 4=10 pole alt, 5=12 pole alt.
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Some tachs have numbered settings like 1 thru 4 or 5 and a small tag indicating what each number corresponds to. As an example (but not necessarily an accurate depiction) 1=4 cyl, 2=6 cyl, 3=8 cyl, 4=10 pole alt, 5=12 pole alt.
I remember the old Force's had a 20 Pole Tach...which is hard to find!
And, yes, that's totally unrelated to your issue Ross...sorry! lol!
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Some tachs have numbered settings like 1 thru 4 or 5 and a small tag indicating what each number corresponds to. As an example (but not necessarily an accurate depiction) 1=4 cyl, 2=6 cyl, 3=8 cyl, 4=10 pole alt, 5=12 pole alt.
That is pretty much what the table on the back of the tach looks like so if its a 12 pole alt, 5 is correct. I wouldn't think it could have moved on its own. You have to use a small screw driver and push it in so I believe it is in the same spot it was all these years
5-12
I am going to mess with it like you said Rich and hook it back up and see what happens.