Coils Arcing

K

Kenny Sorweide

Cadet
Joined
Sep 10, 2004
Messages
21
I was checking for a misfire on my 1975 75HP Evinrude. I did this in the dark to see if there was any arcing. the only time I could see any was when I would pull a plug wire off. Doing this caused a lot of arcing around 2 of the coils. (looks neat at night). The 3rd coil didn't do this. Why does a coil do this when it is unplugged from the spark plug, but not otherwise, and why on only 2 coils? Thanks in advanced for any help on this.
 
Dunaruna

Dunaruna

Admiral
Joined
May 2, 2003
Messages
6,027
Re: Coils Arcing

The discharge from the coil is looking for the easiest path to ground, in a perfect world, this is a the tip of the spark plug. A coil that has the lead disconnected will still look for ground, cracks in the tower are full of dirt and crude - they are often very conductive - hence the light show you saw. The third coil is either not operating or the tower is not cracked.<br /><br />Aldo
 
P

Paul Moir

Admiral
Joined
Nov 5, 2002
Messages
6,847
Re: Coils Arcing

Or it's arcing over somewhere where you can't see it. ;) <br />It might be the source of your misfire. If the coil is apt to arc over, generally it will not produce a spark as long as the others. It's a simple & easy test. Swapping it with one of the others would prove it's the coil rather than what's driving it.
 
K

Kenny Sorweide

Cadet
Joined
Sep 10, 2004
Messages
21
Re: Coils Arcing

Thanks guys. I will change the coils around tomorrow and see what happens. Appreciated the quick reply
 
R

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Coils Arcing

hello.<br /> you already know 2 of 3 are damaged. just replace all 3<br /> its a common jonny rude failure.
 
K

Kenny Sorweide

Cadet
Joined
Sep 10, 2004
Messages
21
Re: Coils Arcing

OK your advice is taken. I will replace all 3. Can I get by with using whatever brand that my local NAPA store sells, or should I stay with OMC ones. I would like to use the boat soon so would like to get them local. I will order some for spares from this site. Thanks again for everyones quick response to my question.
 
P

papasage

Senior Chief Petty Officer
Joined
Jan 12, 2003
Messages
785
Re: Coils Arcing

i have a 1974 70 hp 3 cylinder i use napa oils and have no probablem .
 
You must log in or register to reply here.
Top