Re: 3.0 mercruiser no spark from coil please help!!!
Hey Great ! Glad you got it running.
The coils you are trying to use probably require a ballast resistor. They are getting too much voltage and overheating.
If you have two wires on the + side of the coil one is active in the ON position and the other is active in the start position. The one that's active in the ON/ RUN position is the one the ballast wires inline (in series) with.
Now, if you have only one wire on the + side of the coil, you will either have to run another wire to the + side of the coil from the from the side of the starter solenoid that goes to the ignition switch and gets 12v when starting
and place a ballast resistor inline with the existing wire that was already on the coil. That way the coil gets full 12 volts when starting and when you let off the starter the coil voltage comes from the reduced voltage from the ballast. Comprende` me Amigo ?
Now if that sounds confusing and I know it does because I confused myself a time or two trying to write and understand it myself.....
The simplest thing to do would be to buy an ignition coil that doesn't require a ballast resistor.
Le me do an edit here and include a couple of things that may or may not play a role. If the coil does have 2 wires on the + side and you do locate a ballast resistor already there then you may have the wires crossed on the ignition switch just trace those back to the switch and make the appropriate changes.
Another culprit could be an alternator overcharging but you would notice that on the gauges if they are functioning correctly. Check the voltage at the battery with a multimeter while the engine is running. It should be in the neighborhood of 13 - 14 v no higher than 14.5-15 which is really too high.
Good Luck.
