Johnson J25 ELCTD keeps burning out top coil

[c-dubb]

Does anyone have an idea as to why this motor may be burning out the top coil only? I purchased this motor a few years ago and within a week the top coil went out. I replaced it with the CDI replacement coil and it went out after about a month. I then replaced it with the Sierra replacement coil which lasted about 1-2 months. I then replaced it again with the CDI coil and it lasted about a year and now it is out again. Any help would be appreciated.

 

[racerone]

Pot the " bad " coil on the bottom and see if it fires.----Just as a test.-----Coils do not fail that often and are very reliable.-----Perhaps something else is wrong !

 

[c-dubb]

Pot the " bad " coil on the bottom and see if it fires.----Just as a test.-----Coils do not fail that often and are very reliable.-----Perhaps something else is wrong !

I did this each time just to verify that the coil was in fact bad.

 

[Joe Reeves]

There are two "M" terminals on the back of the ignition switch (if used) one of which is raised higher than all others.

The only wire to be attached to that "raised M" terminal is a "Black/Yellow" wire (the kill circuit.

The other regular "M" terminal should also have just one wire... a black wire running to ground...... Some boaters (many, really) and even boat yard riggers use this regular "M" terminal to attach and ground out their 12v power accessories (not a good idea). The problem this creates seems to vary on whether the boat is wood, fiberglass, or metal... no, I have no idea why.

However, in using that regular "M" terminal of the ignition switch for a ground and when the key is in the OFF position, both "M" terminals are connected... and if some accessory is turned on, the battery voltage cruising through that accessory is still DC voltage as it leaves its ground wire, and since the two "M" terminals are connected, that voltage has access to the magneto capacitance discharge ignition system... and in time, weird things will happen.

Sort of a poltergeist type thing! Perhaps not the cause of your problem, but it's something worth looking at.

 

[F_R]

If not that, then some other fool wiring error. Check the voltages on orange coil wires with engine not running, key in various positions. Should be zero volts (zero battery voltage to coils).

 

[Joe Reeves]

If not that, then some other fool wiring error. Check the voltages on orange coil wires with engine not running, key in various positions. Should be zero volts (zero battery voltage to coils).

In agreement with F_R.... I would also add that on many occasions, the ignition switch will develop a slight internal short that will allow (usually) just a micro-volt of DC voltage to travel to the raised "M" terminal. This normally causes the destruction of the powerpack (over a period of time) but one could assume that it could travel through the pack to a individual coil.

Easy to test... Disconnect the black/yellow wire at the powerpack... key in ON position... check the black/yellow wire on the engine wiring harness side for voltage with the meter set to register even a micro-volt. If "any" DC voltage is present, replace the ignition switch.

 

[Faztbullet]

I doubt stray voltage is causing this as pack SCR would have to trigger stray voltage to just that coil. I have see bad coil wires cause coils to fail as overtighted coils as powdered internal ferrite breaks and not use grounding washers(some people call them star washers)

 

[F_R]

The voltage I speculated (to the orange wire) would not be passing through the power pack nor SCR. It's just a guess anyway. Why not at least slap a voltmeter on it?

But I have seen Universal Magneto coils blown up by somebody grounding an accessory to one of the kill wires, which lead to the coil primary winding on the Universal Mag.

 

[c-dubb]

Thanks for the input guys. I hope to be able to troubleshoot further this weekend, I'll post my findings.

 

[c-dubb]

If not that, then some other fool wiring error. Check the voltages on orange coil wires with engine not running, key in various positions. Should be zero volts (zero battery voltage to coils).

Key off=0 volts, key on=.002 volts DC

 

[c-dubb]

In agreement with F_R.... I would also add that on many occasions, the ignition switch will develop a slight internal short that will allow (usually) just a micro-volt of DC voltage to travel to the raised "M" terminal. This normally causes the destruction of the powerpack (over a period of time) but one could assume that it could travel through the pack to a individual coil.

Easy to test... Disconnect the black/yellow wire at the powerpack... key in ON position... check the black/yellow wire on the engine wiring harness side for voltage with the meter set to register even a micro-volt. If "any" DC voltage is present, replace the ignition switch.

Key off, Black/yellow =0 volts. Key on, black/yellow = .001 volts dc

 

[Joe Reeves]

Key off, Black/yellow =0 volts. Key on, black/yellow = .001 volts dc

And I assume "Engine Not Running", and if so... Normally, that, in time would destroy the powerpack.

 

[c-dubb]

And I assume "Engine Not Running", and if so... Normally, that, in time would destroy the powerpack.

Yes, engine not running. See the “sticky ooozie” stuff near the coils in this pic? It is remnants from the original coil that I replaced. The bottom one has also been doing this the whole time.

 

[F_R]

I was suggesting the orange coil wire, Joe was on black/yellow. Two different circuits, neither is good. But .002V on the orange probably is not enough to blow it up.

 

[Joe Reeves]

If I understand you correctly... it is the "top" coil that has been constantly burning out... and now it is affecting the bottom coil. It seems to me that would be the result of having DC voltage applied to them somehow. Frankly I've never encountered a situation such as this and perhaps other members have... so I'm going to back out of here and hopefully other members will have the answer, and I'll learn something.

 

[c-dubb]

Yes the top coil is the one always burning out, but the bottom coil seems to have been always affected too, but never burned out. It was leaking the sticky stuff from day one.

 

[c-dubb]

Yes the top coil is the one that always burns out, but the bottom coil seems to have always been affected too. It has leaked the sticky stuff from day one just like the original top coil but it hasn’t burned out yet.

 

[c-dubb]

Thanks for all the help guys, put a good coil on it and it still didn’t crank. Got 0 psi compression on the top cylinder now.

 

[racerone]

O compression is not a coil problem-----How did you determine that you had coil problems all along.

 

[c-dubb]

Top Coils were bad each time including this one. I verified with adjustable spark tester and moved wire from bottom coil to top coil to see if the coil would fire. I just assumed that was the only problem this time as well. I guess I damaged something else limping back to boat ramp on one cylinder.