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1977 115 HP - Coil Failure - Ongoing issue

N

nicklanigan

Contributing Member
Hi all,

In 2016 I had a power pack failure - the power pack was one of the original johnson ones - no idea how old it was, but it was pretty old. Up until then, I never had a coil failure - even though 3 out 4 had cracks that had been siliconed over. The new power pack is from CDI.

To avoid a potential future failure, I replaced all 4 coils straight after the power pack - however I've now had 3 coils fail in 2 seasons of boating.

Is this normal?

When the coils fail, they test just fine on an ohm meter, but using either a spark tester or timing light, nothing is being produced.

Plugs and plug wires have been replaced through normal maintenance - no impact - still have coils failing.
 
I'm hesitant to reply because there are several experienced "pros" in these forums and I'm just a hobbyist who has a mixture of wins and fails. Hopefully the coil issues have been resolved during the past 2 weeks. If not, maybe I can help some. I have 2 similar motors: a 1977 Evinrude 85 hp and 1976 135 hp. The coils on the 85 hp have been on there for about 12 years and the engine runs fine. They are the green Sierra coils and have the plug wires"built-in" so to speak. Cracks can form from heat and vibration over time. Last year my 85 hp misfired and there were no cracks in the insulation. I snipped a half inch off each plug wire at the boot end and replaced the oxidized terminals. That solved the misfire. How's the engine wiring harness? If it's a bit crumbly, that could impact coil performance even with new ignition components. Just a thought. I like these mid-70's Johnson-rudes and hopefully yours is in service soon.
 
Quite unusual for one engine to have so many coils fail unless one has been in New Orleans and upset a Cajun Voodoo Practitioner somehow. That'll bring down upon you a coil curse that won't be easily shook! :)

However... New or not, check the continuity of the coils as follows:
(Magneto Capacitance Discharge Coils - Continuity Test))
(J. Reeves)

Check the continuity of the ignition coils. Remove the primary orange wire from whatever it's connected to. It may be connected to a powerpack screw type terminal, a rubber plug connector, or it may simply plug onto a small boss terminal of the coil itself.

Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground of the coil or the powerhead itself if the coil is still installed.

Then touch (still with the red lead) the orange wire if it's attached to the coil, or if it's not attached, touch the primary stud of the coil. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire. Poor or no continuity of a coil is one reason for s/plug fouling.
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Also check for actual battery voltage being applied for any portion of the ignition system. Normally if this happens due to faulty wiring or a intermittent short of the ignition switch, the powerpack is the first thing to be destroyed... BUT... if somehow battery voltage or a portion of that voltage is applied to a coil... that will certainly destroy it.
 
Right. Gotta be a wiring or stator problem. Higher current is getting to the coils to fry them. Can you tell us if they go as a pair, or 1 by 1? What is maximum spark jump with a tester. Is it more than 1/2 inch?
 
OH... the voltage thing... forgot to mention, as follows.... this problem usually fries just the powerpack BUT it's worth mentioning:
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Voltage To Powerpack Failures
(Magneto Capacitance Discharge Systems)
(J. Reeves)

The usual cause of having those type powerpacks fail repeatedly is having a very small of voltage applied to the Black/Yellow wire (Kill Circuit) at the pack. Test as follows.
Disconnect the Black/Yellow wire at the powerpack.

Insert either a ampere meter or a volt meter set to its lowest DC voltage reading between that Black Yellow wire and ground.

With the ignition key in the OFF position, observe the meter reading. Now turn the ignition key to the ON position and again observe the meter reading.

Any reading, movement of the meter needle, even a microvolt, would indicate that battery voltage is being applied to that Black/Yellow wire. If a reading is present, remove the other end of that Black/Yellow from the raised terminal of the ignition switch.

If the reading ceases to exist when the Black/Yellow wire is removed from the ignition switch, replace the switch. If the reading continues to exist, there would be a short of some kind in either the engine or instrument wiring harness.... to determine which, simply unplug the large RED electrical plug at the engine which would eliminate the instrument cable.

Note that the black/yellow wire must not have any other wire attached to it for the following reason!

Keep in mind that any accessory that has 12 volts running to it, especially when turned on, will have voltage flowing thru it and trailing out thru its black ground wire to complete the circuit. If that accessory has it's black ground wire attached to the "M" terminal that the black/yellow wire is attached to.... you will have voltage flowing directly to the powerpack.
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There is no way stray voltage can get to a coil. It would have to go thru pack (killing it)or jump spark gap at plug to reach the coil. Usually it a mounting problem due to the new style coil use a powered formed ferrite. This easily cracks do to over torqueing and failure to use washers and grounding washer(the star). Remember coil gets it voltage from pack which gets its voltage from stator. Make sure your not running resistor style plugs.
 
Last edited:
faztbullet said:
There is no way stray voltage can get to a coil. It would have to go thru pack (killing it)or jump spark gap at plug to reach the coil. Usually it a mounting problem due to the new style coil use a powered formed ferrite. This easily cracks do to over torquing and failure to use washers and grounding washer(the star). Remember coil gets it voltage from pack which gets its voltage from stator. Make sure your not running resistor style plugs.
Click to expand...

Normally..... Yeah, quite true. However, as we well know... not everyone wires normally! :)
 
Right, the stator firing too high output and grilled the first pack, new pack more tolerant and overpowering coils. Aftermarket packs are engineered often for broader imput. What you think?
 
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