Force 125 Tachometer inop

[chrismarion]

Okay, I finally am getting a tach installed on my boat and I am having problems with the signal. Its a 1987 125 with Prestolite Ignition.The tach is a new Faria tach and I turned the switch to #6 which is 20 poles. I searched the forum and did what it suggested on the other topics, but I need more info.
I started the motor and took my multimeter to check for voltage at the rectifier. I grounded my lead and probed the other lead at the tach output, voltage was speratic from 10v to 18v. It was moving so fast up and down I couldnt read a steady number. Same goes for testing the other green/yellow wire coming from the stator, and the red battery wire going out of the stator. All read the same on the meter. The manual does not say how to test the rectifier.
What should I be seeing, a flat value of voltage or slowly fluctuating value? Do I need to do an ohms test? I really want to get this tach operational. Also make sure the stator and rectifier ar operational too. Any tests I need to perform PLEASE let me know, I am electronic literate!

Yes the tach is wired up correctly, but I havent had a tach on this motor. Just now getting to where I can take it to the water for testing.

 

[chrismarion]

Re: Force 125 Tachometer inop

Sorry, typo. The red battery lead is coming from the rectifier! Just to correct myself.

 

[chrismarion]

Re: Force 125 Tachometer inop

I did an Ohms test on the two leads coming from the stator ( green/yellow wires) and the resistance is .08 Ohms.

 

[Frank Acampora]

Re: Force 125 Tachometer inop

I had a 1999, 90hp that the tach did not work on. I discovered that even though the battery was charging enough to keep it full enough for restarts, the rectifier was bad. When I switched to a good rectifier, the tach started working. It probably had something to do with the purple wire (tach on my engine) that connects to one side of the a/c on the rectifier. to test the rectifier use a multimeter. when you connect pos. and neg wires (red and black) to both sides of the a/c you should show continuity. When connected to the d/c terminals, it should show high resistance between the a/c and d/c terminals one way and very low resistance in the other direction (That's how it rectifies) The exact testing procedure is in any Chrysler/Force manual. they are available in your public library. At any rate, if you can get your hands on a known good rectifier, swap them and see it this solves your tach problem.

 

[Frank Acampora]

Re: Force 125 Tachometer inop

Oh! by the way, the rectifier is not regulated so what you get on the red wire is pulsing d/c voltage. Because it is not a regulated system, you need to frequently check battery water level.

 

[Frank Acampora]

Re: Force 125 Tachometer inop

And double by the way-- .08 ohms is about right for your alternator stator. It shows that your windings have continuity-- your alternator is working correctly.

Testing of the rectifier must be done with all leads disconnected.

 

[chrismarion]

Re: Force 125 Tachometer inop

Thank you sir, I will go out and test the rectifier. I have the Seloc Online Manual, but I am slowly seeing that I need to buy the paper copy! Just havent found one locally.
Will post up results when I am done.
Thanks again

Chris

 

[roscoe]

Re: Force 125 Tachometer inop

You said you are having trouble with the signal, but you didn't say how the tach is reacting, if at all. What does the tach do when the engine is running?

Do the wires all connect at a terminal strip, or do the wires have bullet connectors on them?


Check your battery voltage across the battery terminals.

Then start the engine and check it again.

If the voltage is higher with the engine running, the rectifier is doing its job, for the most part. Yes, the rectifying side or the tach signal can go bad independently, but usually it will fail all together.

If the engine runs and fires on all 4 plugs, the stator is working, but you can do a resistance check on the 2 pairs of blue and yellow wires coming from the stator, should be 650-800 ohms.

There is a purple (or grey) wire exiting the rectifier, correct?
That is the tach signal wire.

Attach it to the SIG terminal on the tach.
Connect a wire to the GND terminal on the tach, the other end goes to a ground wire in the wiring harness.

 

[chrismarion]

Re: Force 125 Tachometer inop

Roscoe,
The wires on the tach have the little bolt prongs which are bolted down and not touching. The rectifier has holes in each prong with the eye-lets of each lead screwed in. The Tach does nothing in any position, wether you choose 20 poles or less. I have not tried to check voltage while it is running, but I will tomorrow. It is too late to start it. Yes the ignition system is working perfectly, but I will check to see what the voltage output is while running.

The rectifier has 5 wires on it. Starting at the top of square rectifier going clockwise:
Green/yellow (Stator)
Red (To Solenoid, Then Battery)
Green/Yellow & Purple (Stator & Tach)
Black (Ground on starter)

I have a reading of voltage at the rectifier when it was running, and at the terminal strip too. Just below it. Now the purple wire comes from the Rectifier, to the terminal block, then into the engine harness up to the center console. It is then connected to the take at SIG post. The GND post is attached to a ground block for the entire boat. Should this not be attached at the ground block? And finally the BAT post is connected to the ignition power coming from the battery. Is this not correct?

 

[roscoe]

Re: Force 125 Tachometer inop

Yes that sounds correct.
Any good ground that gets back to the battery, will do.

So, with the engine running, do you get any voltage between the purple wire and ground?

If you are getting voltage in the purple wire, the tach should work.

This may sound stupid but...
If you have voltage in the purple wire where it connects to the tach;
loosen the tach mounting bolts until the tach is a little loose in the hole.
Start the engine and see if anything changed.

Update us with your progress.

 

[chrismarion]

Re: Force 125 Tachometer inop

Ok, Checking the voltage at the batteries with engine off is 12.14v . With the engine running the voltage is the same. Voltage at the engine terminal strip for the purple tach is erratically moving from 10v to 18v, from the terminal strip into the engine harness up to the console at the tach is 6.07v . The tach has 12.14v for power and a good ground with .01ohms resistance. Light on tach also is functional.

The tach is NOT mounted in. It is just sitting in the hole untill I know it is fully functional. No matter which angle I hold it, the needle does not move. Now why at the terminal strip is the voltage erratic, but at the center console where the engine harness ends and goes into the other terminal strip it is 6.07v ??

 

[roscoe]

Re: Force 125 Tachometer inop

Don't know why the voltage stabilizes up the line.

6v is enough to signal the tach.

The battery voltage is more concerning to me.
No increase in the voltage with the engine running, indicates that it is not charging the battery.

First inspect all wires from the stator for cracked/missing insulation that may be grounding out somewhere.

I guess at this point I would get a new rectifier.
Mercury sells them for $36.
Aftermarket for $22, google "rectifier 152-9209"
Some guys have used radio shack parts for about $5.

 

[chrismarion]

Re: Force 125 Tachometer inop

I am cool with the $36, thats not a problem. But what if I am not finding any wiring problems? The manual is stating through the tests that the rectifier is the culprit. The batteries are brand new and not the problem.

Also, I googled that number. It shows up for the 120hp and the 125 is 155-9450. Which is correct?

 

[roscoe]

Re: Force 125 Tachometer inop

If you don't see any obvious wiring flaws, get a rectifier.

Ok, I triple checked and
I've got three sources that say 152-9209

1- The CDI (parts manufacturer) cross reference chart, page 47:
http://www.marineengine.com/parts/manufacturer/2007_CDI_Catalog.pdf#page=47

2- retailer chart: outboardparts (dot) com/chrysler/mall/chryslerforceregulators.htm

3- retailer chart: maxrules (dot) com/fixforcelectric3.html

(dot) was inserted into the address, so as not to provide a direct link to an iboats competitor.

BUT the cheapest source online, is right here on iboats. Here is the link.

http://www.iboats.com/mall/?keyword...138994744&list_time=1170051971&view_id=335815

 

[Frank Acampora]

Re: Force 125 Tachometer inop

There is one other thing you need to check: Because of the wiring and ignition arrangement of these engines, the "I" terminal on the ignition switch is used only for accessories that are used while the engine is running.

Power to the ignition and cd boxes is a dedicated part of the alternator and has nothing to do with the battery charging circuit of the alternator.

Because of this, you could have a bad ignition switch and the engine will start, choke and run ok. However, the tach would either not function or function erratically. And this may only happen while the engine is running due to vibration. To quickly check this, disconnect the power wire to the tach from the "I" terminal and TEMPORARILY hook it up to the "B" (battery) terminal (red wire in cable from engine). This gives you direct power from the battery to the tach. Start the engine. If the tach works properly, you have a bad ignition switch. If you leave this wire hooked up this way, you will slowly drain the battery while the engine is off. Also check your grounds. many electrical problems are caused by poor or faulty grounding.

Alternators are a/c generators and produce a fairly level voltage between low and high speed. Charging voltage for a 12 volt battery is usually between 14-16 volts. Battery voltage with the engine off is acceptable at higher than 12 volts. A brand new battery will usually run between 13-14 volts at the terminals.

To diagnose complex electrical problems on these engines, a regular multimeter is not good enough. You must use a multimeter that is capable of capturing and displaying peak voltage.

This is most likely not a complex problem It is probably either your rectifier, your ignition switch or poor grounding somewhere. You are getting a signal to the tach, aren't you? That signal should come off one of the a/c terminals on the rectifier.

 

[chrismarion]

Re: Force 125 Tachometer inop

Finally reposting after I had some shipping problems with UPS, one month to get a rectifier. Unreal. BTW, this rectifier was purchased new here from iBoats a Roscoe posted.

I installed the rectifier and started the motor. Tach still not working and its not chargng the batteries. Voltage was the same with the motor off. This rectifier came almost identical as the original. I have it wired the same as the old on, except this new one had one side that said AC and then + .
Checking voltage still shows AC side operating as usual, solid ground with .01 ohms resistance. The tach has signal now up at the tachometer. At idle it reads 5.8v on the meter and rev it up quick it went to 18.1v . Normal? I suspect now the new tach is inop. Atleast I have signal at the tach now. Is that a normal Idle voltage? I noticed that on the rectifier side (Battery wire) of the breaker I have 12v on one side and 10v on the other with the motor off. Shouldnt have a 2v drop. Irretating this is. I just want a working tach and charge my battery, is that to much to ask!!:|

General question, when you put it in gear the post moves a lever at the stator (under flywheel).What is its exact function?

 

[Frank Acampora]

Re: Force 125 Tachometer inop

That lever is the timing advance. You will notice that it moves in the opposite direction as the flywheel as you advance the throttle. There is a magnet in the hub of the flywheel. this magnet passes three or four small coils (depending on number of cylinders) carried on the aluminum plate under the flywheel. as the magnet passes each signal coil, they generate a small signal voltage (usually about 1/2 volt) to tell the electronic ignition module to dump its stored voltage into the corresponding spark coil, and fire that plug. As the lever moves, rotating the carrier, the coils advance thus advancing the timing.

Look closely at your rectifier. The diagonal corners should each say A/C and the opposite diagonal corners should say + and - respectively. - should be hooked to ground, and + should have the red wire going to the circuit breaker. From the same circuit breaker terminal another red wire should go to the battery side of the starting solenoid. This is what charges the battery. One A/C terminal should have the purple wire and also one wire from the alternator attached. The other A/C terminal should have the remaining alternator wire attached.

 

[chrismarion]

Re: Force 125 Tachometer inop

Correct on the wires and where they are leading to. But like I stated I do not have a rise in voltage coming from the rectifier. Voltage is the same when its off or running. Must be another reason why its not higher, will have to do some reading.

Is the tach signal that I am showing now meaning its functioning properly? I tried what you said and it didnt make a difference. Hence why I believe the new tach is not functioning. Odd since Faria are good gauges! What is the amount of voltage needed to make the tach needle move some, wondering if I can test it out somehow. I will search for that on here and the web. Thanks Frank.

 

[Frank Acampora]

Re: Force 125 Tachometer inop

If you know anyone else with a Force and they are willing to let you temporarily hook it up to your tach, then you will know for sure.

Try some 16 oz fiberglass handled psycology on that tach---LOL

 

[chrismarion]

Re: Force 125 Tachometer inop

If I could I would break my foot off in it!! Everything else is running smooth, I am very pleased with what I have accomplished. Except for Faria at the moment.