Spark intensity?

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ckraker

Petty Officer 2nd Class
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Apr 21, 2007
Messages
140
135hp 1974 evinrude

inconsistent idle, fouling plugs, hard start, stalls. WOT runs great.
Already replaced plugs, power pack, coils, carbs rebuilt, rectifier tested okay, compression is good.

I have 300 VAC supplied to the power pack, but is that for sure telling me that my stator is working? What about AMPS? My Stator is oozing but like i said my voltages are still good. Also it doesn't run worse when it heats up like other have said can happen with a hot stator. My spark can jump a 7/16" gap but it isn't a fat blue spark its skinny and almost white. Can someone post pics or a video of what my spark should look like?
Thanks everyone
 
danoutbard

danoutbard

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Re: Spark intensity?

If it jumps, its probably strong enough….
Good luck
 
MH Hawker

MH Hawker

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Jul 13, 2011
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5,516
Re: Spark intensity?

Advance auto carried a spark gap tester, it is adjustable for several high voltages so you can test that.

But what your describing is more of a low speed idle and a carb issue, my guess is a worn out needle valve or a bad float.
 
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ckraker

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Re: Spark intensity?

If it jumps it's good. Is it really that simple? I don't need a nice fat blue spark? (i already have the gap tester, that is how I'm watching the spark)

Still hoping for some images or video.

needle valves are brand new. Floats are old....how do floats go bad? They do not
Seem saturated, and why would a bad float foul plugs?
Thanks
 
metriccrescentwrench

metriccrescentwrench

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Oct 22, 2007
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Re: Spark intensity?

ckraker said:
I have 300 VAC supplied to the power pack, but is that for sure telling me that my stator is working? What about AMPS? My Stator is oozing but like i said my voltages are still good.
Click to expand...


You can't use the AC range on a standard meter to test ignition components. You'll need a DVA adapter, what that does is to capture the peak of the pulse (which only lasts a few microseconds) and convert it to a DC voltage that you can read on your meter. They can be purchased for under $50 as I recall, or if you're handy with a soldering iron you can build one for under $10 worth of components. Search online for a schematic.

As far as what values you should be seeing, if you don't have a factory manual check out CDI Electronics site, search around on that and you'll find an ignition troubleshooting guide.

I'd replace that stator, if nothing else some of the stuff that's oozing out of it can interfere with the timer base rotating freely. Plus it's just never a good thing when an electrical component is loosing it's guts.
 
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ckraker

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Re: Spark intensity?

I have a dva. Thats how i measured it.
 
Faztbullet

Faztbullet

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Re: Spark intensity?

What is pack output to coils? Weak output from pack is sign of low voltage from internal capacitor, which means defective pack or low voltage from stator that charges it.
 
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emdsapmgr

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Dec 9, 2005
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11,551
Re: Spark intensity?

Have you hooked up an inductive timing light to see how each spark plug wire is firing when the engine is idling?
 
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ckraker

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Re: Spark intensity?

emdsapmgr said:
Have you hooked up an inductive timing light to see how each spark plug wire is firing when the engine is idling?
Click to expand...
Yes sir, they all fire at idle. And I checked them using your timing light method.

Also output to coils from the pack matches the 300 going in. the power pack is brand new.
Can someone tell me more about my sparks white color, and thin apperance. I believe I read that it should be fat and blue. As seen though the gap tester tube.

Also how can I determine if I have a bad float?
Thanks
 
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oldman570

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Mar 25, 2011
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Re: Spark intensity?

What plugs are in the motor? Are they the ones called for by the manufacture.
Have you cleaned all the battery conections on the motor block and coils on both battery leads.Bad conectios of the electric circut might be the cause of trouble JMO
Oldman570
 
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ckraker

Petty Officer 2nd Class
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Messages
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Re: Spark intensity?

All the connections have recently been apart and cleaned. We aren't running factory suggested plugs, we have gapped plugs that were suggested by......everyone. They are supposed to foul less often, so far we are disproving that theory.
 
Faztbullet

Faztbullet

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Re: Spark intensity?

I would say stator is bad... you can have voltage but no amperage and that will make spark weak. You should only have about 200V at cranking anyway..
 
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ckraker

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Re: Spark intensity?

Faztbullet said:
I would say stator is bad... you can have voltage but no amperage and that will make spark weak. You should only have about 200V at cranking anyway..
Click to expand...
Interesting..... This is sort of what I was suspecting. It jumps to 300 very quickly while cranking which made me suspicious.
 
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dcr42t

Seaman
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Sep 29, 2010
Messages
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Re: Spark intensity?

Well i have just checked my 1977 70hp johnson with a home made dva adapter, with a terminal power pack 3.

I have weak spark when using a spark tester set to 7/16, just as you have described in your first post.
I have 340 volts coming out of the stator to the pack, while the engine is idling, and have the same voltage from the pack to the coils.
The spark isnt easy to see while jumping across the tester, or the spark plug itself. Coils are new.

My motor struggles idling in the water, and wont idle at low rpm. It doesnt like to idle any lower than 10 deg btdc either.

Im thinking it has to be due to weak spark but everything tests ok. Im not sure what to try next.
 
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dcr42t

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Sep 29, 2010
Messages
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Re: Spark intensity?

My 15hp johnson has lightening blue spark with a real crack to it. And thats while rope starting it, and its even more intense while running.
So in comparison, my 70hp has very weak spark.

It would be good if someone could post a vid of a spark test on a 70's motor for comparison.
 
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Rmoore45

Seaman
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Aug 4, 2011
Messages
68
Re: Spark intensity?

Its hard to tell in the video if the spark is weak or not. Is that gap on the tester 7/16"?

Does it spark like that on all cylinders? Compare the spark of that to another cylinder and see if it is the same,better,or worse.

Just a hint, remove all the spark plugs so that the motor can spin freely. I just replaced a coil on my motor that had bad spark, it would just the plug gap but not 7/16" on the tester. I replaced it and now my 115 Johnson runs and idles great.

You could also swap coils and see if it changes. Most likely going to be a carburetor problem by your description.
 
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ckraker

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Apr 21, 2007
Messages
140
Re: Spark intensity?

Just watched the videos! That is exactly what my spark looks like, with brands new plugs, coils and power pack. I'm having the same idling problems as you. Can someone with a well running engine please post a video of
their 7/16 gap jump. I also have good dva voltages.
 
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ckraker

Petty Officer 2nd Class
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Apr 21, 2007
Messages
140
Re: Spark intensity?

Anyone able/willing to post a video of their 7/16" spark tester gap jump? Please? Thanks
I don't want to buy a new stator if I'm going to be wasting my money.
 
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