bad coil???

[jallen22]

I have a 92-94 50hp force That I just recently purchased. The motor fires up easily and idles great but would not reach wot. The rpms sounded low. I dont have a tach just going off of sound of motor. It would only push me about 10mph. I checked compression and compression was great. Did a spark test and no spark on top plug. Good spark on bottom. I swapped the wires to the coils and then I had no spark on bottom but good spark on top. Does this mean I have a bad coil? Could it be another issue causing no spark? Any help is appreciated!

 

[devl]

does that motor have CDI boxes?

 

[scout-j-m]

If you just swapped the wiring to the coils, then your test would prove the opposite...that both coils are indeed good and your problem lies upstream likely in the switchbox or trigger. The next thing to do would be to check all the grounds. Then check the voltage and resistance of the trigger wires. Might as well check the same for the stator while you are at it.

The link below has all the test procedures and voltage and resistance values for your motor.

 

[Jiggz]

When you said, "Swapped wiring to the coils" do you mean swapping the plug wires (from coil to spark plug) from #1 cylinder coil to #2 cylinder coil? Or do you mean swapping the wires from the CDM to each of the coils? You should post exactly what you did. Hint, Swap the coils instead of saying you swapped wires. Then if the problem follows then you know you have a bad coil. If the problem stays on the top cylinder, then the problem is upstream of the coil which is the CDM or even to the trigger. Do the coil swap first and then re-post.

 

[jerryjerry05]

92 they started with Prestolite and then went to Mercury's ignition.
What one do you have?
Pics of the coils??

 

[gm280]

When you said, "Swapped wiring to the coils" do you mean swapping the plug wires (from coil to spark plug) from #1 cylinder coil to #2 cylinder coil? Or do you mean swapping the wires from the CDM to each of the coils? You should post exactly what you did. Hint, Swap the coils instead of saying you swapped wires. Then if the problem follows then you know you have a bad coil. If the problem stays on the top cylinder, then the problem is upstream of the coil which is the CDM or even to the trigger. Do the coil swap first and then re-post.

I second this question as well...

 

[jallen22]

Sorry guys. I had spark on bottom but not on top. I swapped the wires from the cd unit to the coils and then I had spark on top but not on bottom.

 

[Jiggz]

In that case the problem could be the CD unit or the trigger but not the coil. Put everything back as originally wired, Then your next move is to test the trigger wires by switching them around (from trigger to CD units) but you NEED TO MAKE SURE THE PLUGS ARE UNSCREWED and just testing for sparks (meaning the plugs needs to be grounded to have spark) . If the no spark problem stays on the top cylinder then the CD unit is faulty. If the no spark problem shifts to the bottom then the trigger or the trigger wires are faulty.

 

[jallen22]

Im having a hard time figuring out exactly which wires to swap. Here's what I'm looking at. I have one coil out in this pic but you can get the idea.

 

[jallen22]

I took the 4 wires from the trigger and got about 50ohms on two of them and around 2 or three ohms on the other 2. Is this correct Or should I get 50ohms on all 4 wires?

 

[Jiggz]

Resistance reading on trigger wires should be done in pairs with one wire disconnected from the ckt or terminal board, Your motor based on the resistance of the trigger wire you mentioned (50 ohms) is a 92-50 HP Prestolite Ignition system. Resistance should be 48~52 ohms on each pair of wires.

 

[Jiggz]

In one of the pics, I see a white/brown/green wire and next to it is a white/brown/red wire. These two wires are actually a pair and with one disconnected from the terminal board, read between them and you should get 48~52 ohms. While at it, read also from one wire to ground and you should get infinity or a very high resistance. Unfortunately, resistance reading on trigger is not totally accurate. Sometimes even with only one strand of wire still connected, the resistance seems to indicate OK reading but unable to pass voltage. So to make sure the resistance reading is as accurate as it can be, while reading resistance between each pair of wires, try to move, bend and twist the wires and see if the resistance changes. If it does, it is an indication you have a bad wire or connection.

If resistance readings are OK, most likely the cause of no spark is a bad CD unit. Just out of curiosity do you have a wiring diagram to work with? If not I've posted one from some other posts. You might want to save or print it to have something to work with.

 

[jallen22]

Which wires do I pair together?

 

[Jiggz]

I thought I already mentioned the first pair on my last post. So the other two remaining wires will be the 2nd and last pair. Remember these are the wires coming off the trigger unit. In one of your pics (first one I believe) you have a picture of the stator AND NOT THE TRIGGER UNIT. The stator ( in your unit anyways) has the two yellow wires and sets of brown wires. Make sure you read wires off the trigger unit which is located just below the stator. In your second picture with the stator showing I can see the trigger wires coming out (wrapped in white or clear plastic coil wire). Looking at the pics, it's located just left of the stator wires (brown and yellow wires)

 

[jallen22]

Sorry I see it now. I missed that post some how. I sure appreciate the help! I got readings of 49.8 and 49.5. So do I test the stator now? And how is that tested?

 

[Jiggz]

With one circuit of the CD unit working, it's most likely the Stator is also working perfectly. However, if you want to read resistance between the stator power wires (in your case are the brown wires) you can do so and the reading between the set of brown wires should be 680-800 ohms. Note, there could be 4 brown wires coming off of the stator (the yellow wires are for charging the batteries and are connected to the rectifier) and two wires are bundled together for each of the terminal board connections. To read resistance read between each pair of bundled brown wires. Again, disconnect one set of wires off the terminal when reading. If resistance is OK, you most likely have a bad CD unit and need to replace it.

 

[jallen22]

I get no resistance reading at all. Does the fly wheel need to be on and motor cranking to test? And I do have 4 brown wires

 

[Jiggz]

No the flywheel doesn't have to be installed to get resistance readings of the stator. Remember, there are 4 brown wires and they are bundled 2 wires for each terminal connection. Keep the bundled wires together and you have a pair of wires (with 2 wires each). Disconnect one bundled wire from the terminal connection. Place one meter probe on these wires and then the other probe on the other bundled wires still connected to the terminal board. And you should read 680-~800 ohms.

When posting ohms reading, try to post exactly what you read, i.e. zero or infinity or whatever readings you had. Saying you didn't have any readings at all can be misconstrued as either infinity or zero which makes a big difference.

 

[Jiggz]

Anyways, I'm quite sure with the other ckt (there are two separate ckts for each CD unit albeit with common power connections to the stator) on the CD unit working (remember you have spark on the bottom plug but not on the top plug), you need to replace your cd unit. There's no doubt the stator is working since there is only one common power connection for the cd unit's two ckts.

 

[jallen22]

Got an 800 reading on the stator.