Ignition coil test.

BearlyFunctioning

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Apr 15, 2013
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How do I test the voltage output ( eg. 45,000 volt ) of a coil. The back story here is I ordered a distributor kit from a supplier ( not I-boats ) that advertised a 45,000 volt coil in the kit. When it came the documentation said it was a 40,000 volt coil and the part #'s didn't match the packing slip. When they shipped me a replacement coil everything LOOKS identical to the first one they sent me, but no documentation, part #'s or packing slip, just a shipping label to send the other coil back. I'd like to compare the two coils before sending the first one back to see if I'm getting jacked around. Thank you.
 

bruceb58

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Mar 5, 2006
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Basically impossible to test something like this with equipment that most people have. In all honesty, I doubt you would be able to tell the difference anyway. The voltage that the coil will output is a function of your distributor, the spark plug gap and certain other cylinder conditions.
 
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BearlyFunctioning

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Thank you for the simple easy answer bruceb58. I do have a couple more questions. Does it matter if the coil is " copper wound " as advertised, but the coil they sent me has NO documentation one way or the other ? and, What plug gap to run with a new electronic ignition ( Pertronix Flame-Thrower, Ignitor II ) in a stock 1982 228 Merc with a 40,000 to 45,000 volt coil ? Can I increase the gap from stock ?
 
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bruceb58

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Ask Pertronix. If you are using that ignitor, even more reason the coil voltage likely doesn't matter. The stock plugs can only be slightly widened as they are designed to be in a certain range.
 

NYBo

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Oct 23, 2008
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7,107
For testing the coil voltage, apply the 1:1000 rule:
Hook up the coil to the ignition system. While cranking, wet your finger and touch the end of the coil wire to the distributor.

If you get thrown 40', it's a 40,000 volt coil.
If you get thrown 45', it's a 45,000 volt coil.

:faint2:
 

gm280

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There are ways to test the output. But unless you know anything about electronics, I say forget it and happy boating...
 

bruceb58

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There are ways to test the output. But unless you know anything about electronics, I say forget it and happy boating...
I am curious how you would measure the output? Enlighten us!
 

gm280

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I am curious how you would measure the output? Enlighten us!

Honestly Bruceb58. You have to know they sell high voltage probes to use with most any quality meter. And equally so they also sell high voltage probes to use with O'Scopes too. Surely you had to know that...
 

bruceb58

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Honestly Bruceb58. You have to know they sell high voltage probes to use with most any quality meter. And equally so they also sell high voltage probes to use with O'Scopes too. Surely you had to know that...
LOL...yeah, you need more than a knowledge of electronics(your words). You need to buy $200 probes and a meter that has a sampling frequency fast enough to sample an ignition pulse! For an oscope you need $300 probes!

Like I said, "Basically impossible to test something like this with equipment that most people have."
 
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