question on ignition coils..

[Kajun37]

i have 20hp merc 1979...when i got it it had a bad coil and would only run on one cylinder.....so i bought a used one on ebay...and it worked fine, both cyls firing.....have ran it in a barrel a few times over the last couple months...yesterday i finally got to put it on a boat and was going fishing....tested it in barrel before i left and worked fine....get it in water and bam.. back to running on one cyl..same side as it was on the orig bad coil.....swapped the coil wires to see if it was a prob coming from the stator or power pack and everything checked good...so it looks to be another bad coil...

should i just buy a new one? buy 2 new coils....or could there be something that is burning that coil out?

 

[Laddies]

Re: question on ignition coils..

You need to test the system but if swapping the wires on the coils and you still get no fire from that coil it a pretty good sign that the replacement coil is no good that the joy of used parts

 

[Kajun37]

Re: question on ignition coils..

true but i find it suspicious that the same coil/same side that i replaced craps out again.... what would i test to find out if something else is burning them out? the new coils are $61...and i'm going to order 2 of them..would hate to see these news ones get fried also

 

[hkeiner]

Re: question on ignition coils..

While I have never had this problem myself, it has been my understanding that a bad power pack can cause a coil to blow, for example, if the primary voltage sent to the coil is too high. I guess you can continue to replace the blown coils until you confirm there really is a pattern (and not coincidence) or you can use a DVA meter to check primary voltage going to the coil to confirm that it is within spec. I also understand that a bad ground connection on a coil can also cause it to fail.

This is my suggestion based upon my very limited experience in troubleshooting coil problems. Others on the forum may have additional or better suggestions that this.


The following ignition troubleshooting link may also be helpful. http://www.homestead.com/dolphinmarineservice/Ign5.html

 

[ricksrster]

Re: question on ignition coils..

I looked up the specs and it states the DVA voltage should be 180 volts or more. It doesn't state a maximum.

 

[ricksrster]

Re: question on ignition coils..

Check here:
"http://www.boatfix.com/mercag/parts1.asp?partno=481&block=4&img=MERMAR/75538/6.pdf"

 

[j_martin]

Re: question on ignition coils..

I looked up the specs and it states the DVA voltage should be 180 volts or more. It doesn't state a maximum.

A bad wire, or spark plug could cause the primary voltage on the coil to overshoot and self destruct. Otherwise, when the plug fires, it limits the voltages on the coil, thus no listed maximum.

hope it helps