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Ignition coils overheating?

Posted: Jul 5th, '19, 15:59
by pschauss
I came back from a 30 minutes test run this morning (ten minutes each way in the Connetquot River "no wake" zone and about ten minutes out to buoy 28 and back) and checked my ignition coils. Both were too hot to touch. Is this a problem?

Both engines ran fine except that the port engine stalled twice while running at 2500 rpm. I was able to restart it both times.

Stalling at speed has been an intermittent problem with these engines both seasons that I have owned her. Most of the time they restart but I had to call Sea Tow once last summer and twice so far this summer.

This year I have replaced both coils along with new caps and rotors. My starboard engine has a Mallory distributor with the Sierra electronic conversion kit (18-5296-2). The new coil on that engine is Sierra 18-5438 which is described as a ballasted coil.

The distributor on my port engine is Prestolite 7801BS which appears to be a factory electronic ignition, not a conversion kit. The new coil is Sierra 18-5433, unballasted.

Is there some other kind of coil which I should be using with this setup?

Anything else in my configuration that I should be looking at?

Re: Ignition coils overheating?

Posted: Jul 5th, '19, 21:13
by Reelcrazy
are they chryslers? I had Chryslers in my 31. some distributors need ballast resistors some don't

Re: Ignition coils overheating?

Posted: Jul 6th, '19, 05:16
by pschauss
I have 454s but the distributors are not original and the port engine has a different distributor than the starboard engine. Based on the voltage I measured at the coil, the port engine appears to have an external ballast resistor while the starboard engine does not.

Re: Ignition coils overheating?

Posted: Jul 7th, '19, 17:26
by Tooeez
I've had coils get hot like that when I jumped the resistor and fed them 12 volts. As I recall, the older motors with points were wired so that the coil got 12 volts when the starter was cranking, then ran on the lower voltage through the resistor. Maybe someone fouled up the wiring harness and cut the resistor out. Also, motors usually have either an external resistor or a resistor wire--it doesn't make sense to me that one engine has an external ballast while the other does not. If someone removed the external resistor from your starboard engine ( and there is no resistor wire) then it is getting too much voltage; if they added a ballast resistor to the port motor without disconnecting the resistor wire in the harness then it is getting too little voltage.