[Mark from Long Lake]

I had to replace the coil on my 1998 4.3 Thumderbolt, I lost the diagram I drew of the coil.
There are 3 wires, it seems like:
Black to -
purple +
Does the gray go to + or -?

Thanks,
Mark

[ColoradoDiablo]

Gray goes to tach signal. Negative side of coil.

[Mark from Long Lake]

Thanks, I thought so but couldn't remember to save my life!

[Mark from Long Lake]

I replaced the coil which was rusty on the back side and the ignition wires. The fuel pump is functioning and there is fuel to the carb. I bypassed the "kill Switch".
I don't think it has spark. What should I check next?

[Mark from Long Lake]

The engine serial number is 0L037602
1998 Mercruiser 4.3 with Thunderbolt Ignition

[mikeyt]

Did you make use of our Starting Troubleshooter Sticky??

[Mark from Long Lake]

I went through the Starter Trouble Shooting as Mikey suggested just to be sure. Everything is working ignition switch, neutral start swith, slave solenoid, starter, fuel pump. But there is no spark. I replaced the coil, there is power to the coil, but no out put. Is there a way to test the new coil? Is there an ignition wiring diagram...is it possible the replacement coil is bad?
Thanks
Mark

[ColoradoDiablo]

Do you have power to the coil while cranking?

[Mark from Long Lake]

Yes to the positive side of the coil and the ground is good.

[ColoradoDiablo]

Faulty coil or Ignition Control Module it sounds like.
What voltage do you have at the coil? Should be 5-8 volts going in if I remember right.
Use a multimeter:
You can test the primary circuit(power in) , it should be between .6-.8 ohms.
Secondary circuit(high voltage terminal) should ohm out between 9.40-11.70 ohms.
If out of range the coil is bad , if within limits , Merc manual says to replace Ignition Control Module.