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Discussion Starter · #1 ·
I have a 1991 Mercury Force that has been incredibly reliable the 8 years I've owned it. This past fall it stopped working. I replaced what I thought might be causing the problem and nothing worked. My boat is in Corpus Christi and no one there wants to work on a motor over 10 years old, however I was told to try Chris Marine in Aransas Pass. I did. They kept it for several weeks and $125 later I was told it was either the fly wheel or the voltage regulator. The fly wheel was only 3 years old and the regulator was brand new. I replaced both and still nothing. Incredibly disappointed in the work they did NOT do and what I was charged for basically worthless information.

To date almost all the electronic parts on the boat and motor have been replaced. The ignition switch, the voltage regulator, all three coil pacs, Stator assembly, trigger assembly, plug wires, and spark plugs. The kill switch system is working. When I look at the schematic the only thing I can see that might be a problem is the ignition harness assembly. There is power to the engine and power to the voltage regulator. But, there is no spark.

My dad and I have been working on this but we aren't used to boat motors or working on boats, just cars so we are stumped. Does anyone have any ideas or know of anyone who can track down the problem and fix it?

I missed fall fishing, winter fishing, now spring fishing. Would really like to go at the end of the spring and beginning of the summer so I need it fixed asap and am incredibly frustrated and at a loss on what to do.

Thanks for any help.
 

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archTech
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There are a couple yellow wires that go between the rectifier and stator with bullet connectors...you should see them in the bundle between the rectifier and starter, below the fuse and behind the starter solenoid. This is where mine are but your's may be in a different place...see attached picture for a Mercury 60 pic. Look for obvious burnt wires and then pull the bullet connectors apart and look for corrosion.

When you say it stopped working...did it die on you or just not start one day?
 

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Discussion Starter · #3 ·
There are a couple yellow wires that go between the rectifier and stator with bullet connectors...you should see them in the bundle between the rectifier and starter, below the fuse and behind the starter solenoid. This is where mine are but your's may be in a different place...see attached picture for a Mercury 60 pic. Look for obvious burnt wires and then pull the bullet connectors apart and look for corrosion.

When you say it stopped working...did it die on you or just not start one day?
Thank you. Yes, it literally would not start. I replaced the regulator first and weirdly it started right up--this was several weekends later. I thought that was it. Fished for a few days then out on the water one afternoon it wouldn't start. Had to have it towed in and it hasn't started ever since, even after replacing almost everything on it.
 

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archTech
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Thank you. Yes, it literally would not start. I replaced the regulator first and weirdly it started right up--this was several weekends later. I thought that was it. Fished for a few days then out on the water one afternoon it wouldn't start. Had to have it towed in and it hasn't started ever since, even after replacing almost everything on it.
Look at those wires and connections as aforementioned...
 

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Check with a dc volt meter and make sure the cdi coil packs are getting 12vdc with the key on. You may have hit on something with a bad wiring harness from the key switch to the engine.
The power should be on the purple wire with the key on.


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Cdi is my bet, that controls spark if all the other compenents check out good. Also look over all the grounds for loose or corrosion. From what ive read/heard you cant really check a cdi to be bad unless u have a known working one and the swap makes it spark. I went thru 3 on my old yamahammer after my spark died, but they were all used and brand new cdi fired it right up.
 

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Discussion Starter · #7 ·
Cdi is my bet, that controls spark if all the other compenents check out good. Also look over all the grounds for loose or corrosion. From what ive read/heard you cant really check a cdi to be bad unless u have a known working one and the swap makes it spark. I went thru 3 on my old yamahammer after my spark died, but they were all used and brand new cdi fired it right up.
That was the first thing I replaced. And after I did the motor worked, then after a few trips it stopped working. It was a brand new module so I figured it was something else.
 

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If your grounds are loose or corroded it cannot complete the return path. Double and triple check those all the way to the battery. Especially if its been around any saltwater, check the block grounds all the way down to crimps on the wires, ive troubleshoot these issues to find a corroded crimp and bad wires, and with a motor that old it can and will happen quick, copper hates salt air/water
 

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I know im a good poke away but if all else fails bring it up to me in kyle id be happy to give it my best to get u back fishin
 

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Discussion Starter · #10 ·
If your grounds are loose or corroded it cannot complete the return path. Double and triple check those all the way to the battery. Especially if its been around any saltwater, check the block grounds all the way down to crimps on the wires, ive troubleshoot these issues to find a corroded crimp and bad wires, and with a motor that old it can and will happen quick, copper hates salt air/water
Am going to check on that today, thank you! The cdi module has been replaced several times now so that it not it.
 
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