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1978 mercury 70hp

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daviejj

New member
I have a 1978 mercury motor, 70hp 3 cylinder. I do not have spark at any of the 3 plugs. I put a new power pack on the motor about 3 yrs. ago. Now there is no fire at all. Could this be the same problem or hopefully something else? Can anyone advise what else to check, or how to check? The motor ran great for some time, although did not use very much.

Warm regards,
Ron
 
Disconnect the "kill wire" on the switch box (black with a white tracer) and see if that works. If still no spark, you might have a dead stator.

Jeff
 
fastjeff said:
Disconnect the "kill wire" on the switch box (black with a white tracer) and see if that works. If still no spark, you might have a dead stator.

Jeff
Click to expand...
Thanks Jeff. The switch box does not have an external kill switch on it. It is an older one. With no spark, could this be the stator?

Thanks again, Ron
 
Could be the trigger, could be the stator, could be the box. Hard to say, but CDI Electronics does have a section for 3-cylinder ADI engines which should help you narrow-down the problem. You're gonna need a VOM at minimum and perhaps a "DVA" adapter for high-voltage readings.

One last item not mentioned is ignition coils. These old coils are notorious for going bad. I got a 50hp in last year that had 3 out of 4 coils shot and the working one was cracked. Replaced all the coils and it ran like new! Not saying that's your issue, but something to consider if you can't find any other reason for the no-spark condition.

http://www.cdielectronics.com/support/

I'd recommend downloading the .pdf file, the online version is a bit "clunky" to thumb through.

HTH.........ed

p.s. even when you have a control box with no "kill" laynard switch, the ign switch shorts out the "kill" terminal on the power pack to kill spark. So the O.P.'s advice to disconnect the kill wire at the pack is still valid. A bad ign switch or grounded kill wire (or bad "Mercury" switch) can kill spark just as well as bad ign components.
 
The kill wire I'm talking about is on the switch box, second wire from the left on the top row. (Black with a white or yellow tracer.) It goes to the remote controls and, if there's a short somewhere (or ?) it will kill the ignition. Disconnect it and see.

Jeff
 
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