Reoccuring Ignition Switch Magneto terminal burn up

[brusk]

I posted a few years ago about this and thought I had it fixed but looks like I didn't. I've had this reoccurring failure usually right after starting the boat, not always on the first start, where the back of the ignition switch smokes and the boat won't start back up. It does crank and the choke still work but it will not fire. I was using a Sierra switch and noticed that the Magneto connector arced from one terminal to the other. I switched back to an OEM switch and sprayed the back with plastidip and was hoping that was the fix as it seemed to work for about a year. I took the boat out this morning and as soon as it started the switch smoked again and was toast.

After getting back to the house I pulled out a spare switch again and started looking at the burned switch along with an old burnt one I kept. The inside of the switch isn't getting burned up even though you can smell burnt on the back of it. I hooked up a bad old switch and it even worked again. So it doesn't actually seem to be frying the switch maybe just burning the back of the terminal some how. I measured the voltage for the magneto wire and it's running at almost 1000 volts.

Only plan of action I can see right now is to clean and check each connector. Load test each wire. Add some dielectic grease to make sure its got a good contact. Currently the only preexisting issue I have is the dual mode timer base has cylinder #5 not working on cold start. Can't say if this would cause any weird issues. The timer base is only a few years old but unfortunately was faulty from the factory.

Any suggestion would be greatly appreciated.

Edit: 89 Evinrude 150 XP

 

[Joe Reeves]

Assuming that your battery is a normal 12 volt battery... my thoughts for this problem you're having of constantly blowing the ignition switch apart would be due to having bare terminals too close to one another OR you're using the switch as a terminal board in connecting wires to it that have no business being attached there.

In my 30+ years experience, this is the absolute only occasion I have ever encountered anyone with this problem. Something has got to be wired out of the ordinary for this to take place.

 

[brusk]

Doesn't make sense. Only wires I have on it are the ones that should be there, any other accessories are ran off the fuse panel which is completely separate from the motor controls. Battery is newer and supplying a good 12.4- 12.5v currently.

I've been through about 8 switches in the last 3 years. I covered the terminals good this last time with plistidip and tape thinking the arcing was the problem. I've checked each wire several times but it seems almost impossible to wire it up incorrectly. Only 1 connector for each. Choke works, starter works, turning off grounds the magneto connection that only leaves one wire for the ignition. Bad thing is as long as it can take to reoccur I might not know if I fixed it for another few months which could lead into next season.

 

[Joe Reeves]

Yes, you are correct... it doesn't make sense. What engine, (make, year, hp) are we speaking of?

Note that the OMC/Bombardier switches I'm familiar with have one "M" terminal raised, such as a small tower. It is the Black/Yellow wire (Kill circuit) that is to be attached to this raised "M" terminal.... specifically attached to this particular raised "M" terminal for some reason.... never explained by OMC or Bombardier to my knowledge.

Obviously battery voltage of 12v will not jump the distance from one "M" terminal to the other "M" terminal... BUT... voltage being fed to the s/plugs from the coils (approximately 50,000v) certainly would. This makes me wonder if a wire (ground wire?) at the engine is missing or loose, resulting in this weird happening somehow... OR... some other wire loose or routed wrong?

The switch has six (6) terminals marked as follows..... what color wires are attached to each terminal?

Raised - - - "M"
Regular - - - "M"
Battery - - - "B"
Choke - - - - "C"
Accessory - "A"
Solenoid - - "S"

 

[brusk]

Yes, you are correct... it doesn't make sense. What engine, (make, year, hp) are we speaking of?

Note that the OMC/Bombardier switches I'm familiar with have one "M" terminal raised, such as a small tower. It is the Black/Yellow wire (Kill circuit) that is to be attached to this raised "M" terminal.... specifically attached to this particular raised "M" terminal for some reason.... never explained by OMC or Bombardier to my knowledge.

Obviously battery voltage of 12v will not jump the distance from one "M" terminal to the other "M" terminal... BUT... voltage being fed to the s/plugs from the coils (approximately 50,000v) certainly would. This makes me wonder if a wire (ground wire?) at the engine is missing or loose, resulting in this weird happening somehow... OR... some other wire loose or routed wrong?

The switch has six (6) terminals marked as follows..... what color wires are attached to each terminal?

Raised - - - "M"
Regular - - - "M"
Battery - - - "B"
Choke - - - - "C"
Accessory - "A"
Solenoid - - "S"

Raised M = Black/Yellow
Regular M = 3 Gray Wires
Battery B = Red
Choke C = Purple with white stripe
Accessory A = 2 purple wires
Solenoid S = Black or Gray hard to tell

Ground at the engine is good and tight. I found this to be slightly loosened last year. Went over everything else on the engine and seemed to be tight and secure. I'll go out after work today and pick up a 50 watt headlight to use for load testing each wire.

 

[jakedaawg]

If I may interject...

I have had this happen once. It was a mid 90's 40hp. I found the amphenol connector at the power pack had corrosion and generally bad shape of wiring in that area.

Solution was a new wire harness at customers request. This solved it. I believe the existing harness could have been satisfactorily repaired, bit customer wanted new. It did solve it.

 

[Joe Reeves]

Be sure to look into the information that "Jakedaawg" had to offer above... a weird happening for sure,,, BUT... that's exactly what you have!

Raised M = Black/Yellow
Regular M = 3 Gray Wires <---------- ???
Battery B = Red
Choke C = Purple with white stripe
Accessory A = 2 purple wires
Solenoid S = Black or Gray hard to tell <---------- Normally white (fades over the years)

Normally there is but one black wire leading from that "M" terminal to ground which completes the grounding of the ignition circuit when the key is in the OFF position which effectively shuts down the engine.

I'm assuming that one of those "gray" wires leads to ground for the above purpose.

The other two "gray" wires..... I suspect that these are ground wires leading off of a couple accessories. Following is a clipping from another trouble shooting area of my database:

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.

Now, whether this pair of improper ground connections would cause your problem, I don't know, but it's something to take into consideration. I prefer the grounding of accessories to be grounded to one point that leads to the negative battery terminal, fuse block usually..Yes, I'm aware that the grounds all end up at the same place eventually... BUT... those "M" terminals have always proven to be rather touchy (for lack of a better word) with this type ignition.

Let me know where those gray wires lead to... and whatever else you might find.

 

[brusk]

Finally was nice enough to work on the thing today. Going over the wiring I found the 2 purple wires were ignition coming from the motor and also going to the Tach so that one made sense. The 3 wires for the ground were 1 ground to the motor, 1 ground to the gauge lights that looked factory and 1 unkown. The unkown came from the factory harness but now clue what it was as it didn't test out for a ground. I load tested each wire with good results, cleaned them, greased them and screwed everything in good leaving the unknown wire unhooked. Everything seems to still work but no clue how many times it will take before I have any issues again.

 

[oldboat1]

Doesn't the tach get a grey pulse wire? Sounds crazy, but can you pinpoint the heat? It's hot enough to provide a serious burn at some point, so an IR gun might help diagnose (I've successfully done that to isolate a short in harness.)

 

[Joe Reeves]

... I found the 2 purple wires were ignition coming from the motor and also going to the Tach so that one made sense.... The 3 wires for the ground were 1 ground to the motor, 1 ground to the gauge lights that looked factory and 1 unkown. The unkown came from the factory harness but now clue what it was as it didn't test out for a ground. I load tested each wire with good results, cleaned them, greased them and screwed everything in good leaving the unknown wire unhooked. Everything seems to still work but no clue how many times it will take before I have any issues again.

The 2 purple wires attached to the "A" terminal = One 12v purple wire powering the tachometer.... One 12v purple wire powering the warning horn (hopefully), you don't say where it leads to.

The rest... you lost me. I have no idea what that means, sorry.

 

[brusk]

Doesn't the tach get a grey pulse wire? Sounds crazy, but can you pinpoint the heat? It's hot enough to provide a serious burn at some point, so an IR gun might help diagnose (I've successfully done that to isolate a short in harness.)

From what I can tell it doesn't seem to run hot, when everything is good it's good. When gets fried it seems maybe something gets overloaded. The burn marks are on the Magneto raised M terminal. With the Sierra switch that didn't have the raised M terminal just a normal terminal I could see arching from the Magneto over to the nearest terminal. Looking over the switches it seems to only be affecting the external parts of the terminal as it looks good internally and still functions when I take it off.

 

[brusk]

The 2 purple wires attached to the "A" terminal = One 12v purple wire powering the tachometer.... One 12v purple wire powering the warning horn (hopefully), you don't say where it leads to.

The rest... you lost me. I have no idea what that means, sorry.

Sorry I was basically saying all the wires seemed to be going where they were supposed to and tested fine. I don't remember but would assume that wire goes to the alarm as it still works with the key on only (had a few recent overheat alarms). The main wires in question were the ground wires, which one seems to be possibly not needed as I'm not sure where it goes. I really don't want to unhook everything from under the console and cut open the harness to trace one wire.

 

[brusk]

Said screw it. Ordered a new timer base for 270. Mine has the 35 Amp system with the Quickstart that has two sets of ignition timing. One set under 96 degrees, that's the one that has a dead #5. Once it warms up it runs fine. Maybe somehow it's back feeding into the ignition switch.

 

[Chris1956]

Arcing means high voltage. 12 VDC does not jump an air gap. Maybe powerpack is feeding voltage thru kill wire?

A absolute guess on my part, but the high voltage has to come from somewhere.

 

[Joe Reeves]

From what I can tell it doesn't seem to run hot, when everything is good it's good. When gets fried it seems maybe something gets overloaded. The burn marks are on the Magneto raised M terminal. With the Sierra switch that didn't have the raised M terminal just a normal terminal I could see arching from the Magneto over to the nearest terminal. Looking over the switches it seems to only be affecting the external parts of the terminal as it looks good internally and still functions when I take it off.

Apparently, or so it would seem, you are the only one on the planet with this problem.... I wonder if there's an award for that?

Normally when the engine's running, voltage/amperage/current, whatever one wants to call it, builds up and flows through that black/yellow wire. Why that happens I don't know, and in the past I could never get a satisfactory answer out of any OMC rep... the most common answer was sort of "It's the nature of the beast"... translation... they don't know either!

Anyhow, when the engine's running, that particular raised "M" terminal isn't connected to anything... and when one turns the key to OFF, that "M" terminal is grounded (the voltage dissipated) which effectively kills the ignition and shuts down the engine.

Should that black/yellow wire be disconnected (test purposes, whatever) with the engine running... and shut down by other means... and you (or someone) grabs the terminal of that black/yellow wire, you would receive a shock equivalent to what is normally available at the spark plugs... makes ones mouth shout all kinds of strange words!

It would seem that somehow the powerpack is building up excessive voltage in that black/yellow wire... enough to cause it to jump/spark to the nearest terminal that would eventually lead to ground. Why?... I have no idea! I can only speculate a internal powerpack problem... OR... a loose ground, a tight but dirty (corrosion) ground connection, or a non existent ground (missing wire). Personally, I'd like to know why this is taking place as much as you do.

EDIT: As an afterthought.... In years past, there were customers that would complain about getting a mild shock when they touched the key. That was always due to a poor or non existent ground of some kind at the powerhead.