1988 Force 125 Negative Voltage CDI

[kf7strng]

Hello,
I hope someone here can help me really fast! I have a 1988 force 125. I recently replaced the CDI module that fires cyl. 3&4. Boat actually runs WORSE now than before we changed it! I know that changing that cdi was the correct thing to do, because we swapped packs from the 1&2 cylinders, and made them run 3&4, and vise versa. the problem followed the bad pack. (I.E. problem was on #4, but moved to #2 when we swapped).

Now, onto my current problem. After swapping, cylinders 1,2, and 3 all don't seem to "run the show", pulling the spark plug wire off of ANY of those while the motor is running has little or no effect on the operation of the motor. HOWEVER, pulling the plug wire on #4 IMMEDIATELY and swiftly kills the motor, kills it so fast that you wouldn't have enough time to attached the plug wire again to keep the motor running. I also checked the stator for the required resistance (a MINIMUM of 675 ohms) which it passed.

Next, I attempted to check the voltage from the CDI module. The Clymer manual states that the output voltage should be a minimum of 220 volts or so. I will admit i do NOT have the DVA for my multimeter, but I don't believe it matters, as on average, most of the pulses I could see were between 800-1000 volts. Either way, cylinders 1,2, and 4 behaved the same when "attempting" to measure voltage from the cdi module. Here's the part that makes me believe that there is a huge screw up somewhere. when testing cylinder #3, the voltage measured is a NEGATIVE voltage! and the voltage was no where near what it needed to be. The reading was about negative 3 or so (-3) Now I find that highly odd, and that is likely the cause of my problems.

Why would my new box be causing problems? the box is the CDI 116-8301 seen here; http://www.marineengine.com/parts/c...ineengine.com/parts/cdi_electronics/index.htm

and here is the PDF for the specs and wiring info: http://www.marineengine.com/parts/technical_information/cdi_116-8301.pdf

I hooked the cdi module up per the specs for 4 cylinder engines in the PDF. Is it possible that the new pack is faulty? ANY feedback regarding this problem will be greatly appreciated!

 

[pnwboat]

Re: 1988 Force 125 Negative Voltage CDI

Be aware that a bad CD module can cause the other good CD module to appear bad. Replace the CD module for cylinders 1 & 2 with the one you took of that was on 3 & 4. See what happens.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

Be aware that a bad CD module can cause the other good CD module to appear bad. Replace the CD module for cylinders 1 & 2 with the one you took of that was on 3 & 4. See what happens.

so, if i am inderstanding you, if i replace the pack firing 1 and 2, with the original one that i had running 3 and 4 before eing replaced, i should see some sort of different condition in the motor if it is that pack, and not the new pack causing problems, correct?

 

[pnwboat]

Re: 1988 Force 125 Negative Voltage CDI

Yes. There is still something not right with your ignition system. The likelyhood of the new CD module being bad is low. After you installed the new CD Module that drives 3rd & 4th cylinder, and results was not good, you need to try and verify what's good and what's bad by process of elimination. You mentioned that when you pulled 1 & 2 spark plug wires one at a time, it had little or no affect on the motor. That's why I would suspect that module is not right. Who knows, if you swap it out and loose #2 cylinder. That would indicate two bad CD modules. Anyways, check it out and see what the results are.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

OK. I still have to try to swap out the boxes. Today My dad and i went on adventure and removed the flywheel. (we have never had it off of this motor). we found that the shaft was rusty, and the flywheel came off hard, we cleaned the post, and the hole in the flywheel, and when we re attached it went on beautiful.

While we had it off we inspected the flywheel and stator, everything seemed ok there. Also before doing this I tested to see if there was power to either kill circuit, and both @ the same time. I couldn't find a problem there ( although when I tested it the first time, i did it WRONG, and tested the kill wires while turning the engine over, THEN there was power at the kill wires).

Anyway, before I go any further I will swap the boxes like you suggested. I will get back to you probably tomorrow night with the results. THANKS again for your assistance.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

Hello,
pwnboat; I swapped the cd module from 1&2 with the one i removed from 3 and 4 previously. Same result, cylinders 1,2, and 3 have little or no spark, and have little to no effect when the plug wires are removed. this leads me to believe the problem now lies else where. I have ordered the sierra 530 multimeter with built-in DVA to test out the electrical system for sure though.

The meter won't be here for a week or 2 though, so i am just guessing, but i believe the problem has to be either the stator, or the trigger. I'm goinng to have to read the manual again and familiarize myself with the procedures for testing both again. In the mean time, if you have anymore advice I am opn to any suggestions.

 

[pnwboat]

Re: 1988 Force 125 Negative Voltage CDI

Well that seems to have eliminated the CD modules. I would begin to suspect the wiring. The wiring diagrams on the .pdf document show not only the wiring for the CDI CD module, but also for the CDI stator and CDI trigger. The CDI trigger only has four leads as the original has eight. The CDI stator has the same number of wires and color code. The wiring for the CDI components is slightly different than the original components, especially the trigger. Do you have a diagram of the original wiring for the trigger? If you are mixing original trigger with a new CD module, you cannot wire it exactly as the diagram shows. Kind of misleading.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

Well that seems to have eliminated the CD modules. I would begin to suspect the wiring. The wiring diagrams on the .pdf document show not only the wiring for the CDI CD module, but also for the CDI stator and CDI trigger. The CDI trigger only has four leads as the original has eight. The CDI stator has the same number of wires and color code. The wiring for the CDI components is slightly different than the original components, especially the trigger. Do you have a diagram of the original wiring for the trigger? If you are mixing original trigger with a new CD module, you cannot wire it exactly as the diagram shows. Kind of misleading.

If the trigger s the original, yes, i have the clymer manual for the force motors up to 150 hp. I downloaded the manual for the new cdi and installed it as per those, and left the trigger wires where they were originally. can you elaborate and tell me where the problem might lie?

 

[Frank Acampora]

Re: 1988 Force 125 Negative Voltage CDI

If the flywheel is turning at about 300 RPM or better, the magnets generate an AC voltage of about 250 volts in each set of windings (there are two discrete sets of windings in addition to the alternator windings.) Since the windings are discrete, you need to be certain that a paired set is attached to a single box for best operation.

I have never tried it, but I suppose that an unpaired set would also work; the AC doesn't care where it is going, as long as it has a place to go. That's why on the three cylinder engines, the two blue stator wires are connected to the same terminal.

The positive half of the 250 or so volts AC charges one capacitor in the CD box. this services one cylinder. The negative portion of the sine wave charges the other capacitor. Thus: there is a positive and negatively charged capacitor in each box.

The trigger actually sets the timing and signals a switching transistor (with a low voltage) to dump the capacitor into its respective coil. This generates a sharp power pulse and a magnetic field in the primary coil winding. The power pulse drops off so fast that the magnetic field collapses through the secondary of the coil and generates 20-60,000 volts to fire the plug.

NOW: I don't know the exact mechanics of it but there is a ground wire for the CD box internals AND a separate ground wire for the kill circuit. Both CD boxes and all four coils MUST be grounded for proper operation. On the original black boxes, the kill wire is the white wire. Short it to ground and the engine stops. On some of the blue CD boxes, the kill wire is black with a tracer AND it is too short to reach the terminal board on the engine near the starter. So, it could be confusing and improperly connected.

If you use the wrong wire for ground, you will effectively be turning off that whole CD box.

SO: Since you did move CD boxes and since you did install a new one, you need to double check the wiring on the side terminal strip of the electronics mounting board, AND you need to be certain that you have a good ground from the mounting board to the block. I also like to "daisy-chain" a ground wire from each CD box and coil to a block ground. -- The electonics mounting plate is mounted on rubber vibration isolators and has no intrinsic ground, I just don't trust it.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

Frank,
Thank you for that information. Yes, My system is a "Prestolite" with BLUE coils, and BLUE CD Modules. I Think i grasp most of what you said. On my STATOR there are two Yellow wires, and 2 blue wires, additionally there are 2 green wires with a yellow tracer.

Now, suppose someone were to remove the yellows, and blues from the terminal block. is it at ALL possible to connect them wrong? I know that say Cylinder #4 takes a yellow, and #3 takes a blue,#2 is yellow, and #1 is blue. How, when looking at the stator can you tell which wires go to which cylinder, or doesn't it matter as long as they get the proper color?

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

looks like its going to be the stator. tested it out with my new meter last night and it was bad. i will let everyone know for sure when i find out.

 

[jerbear56]

Re: 1988 Force 125 Negative Voltage CDI

There is a stacked magnet riveted to the underside of the flywheel. If you or someone previous tightened the puller bolts too deep it can get warped and cause exactly the problem you are having. With the cd pack firing correctly, you may be able to see a burn mark on it. So be sure to check that when you have the flywheel off. And good luck!

And if it's okay with you guys, I'd prefer not to go into how I learned about this particular....uhhh...phenomenom.............

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

magnet seemed to be a little oblong on one side, but after swapping the stator with a new one proper fire returned to all four cylinders. testing on open water tonight. will post results afterwards.

 

[pnwboat]

Re: 1988 Force 125 Negative Voltage CDI

Great news! Let us know how it works.

 

[kf7strng]

Re: 1988 Force 125 Negative Voltage CDI

Well, BAD news. While ALL four cylinders seem to be handling the load equally, the boat just doesn't seem to want to get up off of its butt and go! There IS a fuel delivery problem as the little plastic things on the side are leaking gas from the gaskets, but even squeezing the bulb has no effect at high OR low throttle.

I am beginning to suspect something isn't quite right with the timing. So far we have replace the stator with a brand new unit from CDI Electronics (176-3095), one new CD box from CDI Electronics (116-8301), and put a new prop on it a 13 pitch 14 diameter I think it is. (definitely a 13 pitch though). I read somewhere before that if your timing is off even .0005 inch (yes less than one THOUSANDTH of an inch) that it will throw the timing off 2 degrees at WOT ( I believe thats what it said).

The tach acts odd too, it seems to be at the right range when at ILDE, but at WOT it buries @ 6000RPM (which is 500RPM over the MAX recommended for this motor) how many pules should this tach be set at? again this is a FORCE 125 model 1251x88c ( or just x8c, both are one in the same).

Sometime in the next few days I am going to go over the electronics again as I finally got the darn DVA meter that the book insists on having. I will check EACH component and post the results in ONE post so everyone doesn't have to jump from post to post to get info. Any other thoughts guys, or is it time to move on to timing this beast?? OH! MAX speed was about 8 today. a far cry short of what it SHOULD do on a 21ft Bayliner. I think 38-40 shouldn't be out of reach with only 2 guys on it!