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Merc 50 kill switch trouble

J

Jim73

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I have a 2010 50 hp 2 stroke mercury. Looking for help testing electrical for key switch and kill switch neither will turn motor off. Thank you
 
Assuming the 8 pin Commander 2000-3000 control pinout, used with many HP engines and types of Mercs:

Pin 1: Connects to trigger circuits in engine......supplies kill function when desired, to stop engine.
Pin 4: Battery neg input to control box/ignition switch OFF position, and lanyard kill switch, both to short out (kill) triggers and stop engine.

Ignition lanyard safety kill switch: Shunt grounding of black/yellow trigger kill wire.

My guess is that your black/yellow wire interconnecting the control box to the engine is not making contact, or internal to either, not making contact. Corroded terminal would be the first guess. Second guess would be chafed into by non conducting (to battery ground) boat wiring harness. By not making contact it cannot short out triggers (grounding signal) when required.
 
The blk/yel wire is connected to the trigger signal emanating from the stator under the flywheel but physically connecting inside the CD module. It shorts out (to battery -, aka ground) the trigger such that the SCR that would normally conduct, shorting out the pulse capacitors and causing a spark to be delivered to the plugs, doesn't occur.

There is 12v applied to the ign. switch on the red wire from the engine to the remote control box and from the control it is "switched" to external circuits on the purple or red/pur wire and is referred to as "switched 12v" when the ignition sw. is in any position but OFF. Function is to be able to turn off power to aux circuits like dash lights, gauges, and such when the engine isn't running....keeps from running the battery down when not in use. That is not associated with this circuit.
 
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I did have time today to check continuity from closet connecter at key switch(about 12 inches away) . To motor on black yellow wire first connection after harness and sowed good.
 
Go to the black/yellow wire in a CDM connector and pull the connector off the CDM. Put an ohm meter lead on that pin, with that wire in the wiring harness connector that you removed, with the other Ohmmeter lead going to a shiny spot on the engine block. Ignition switch off. Lowest Ohms scale. If you are good to go the meter will read zero ohms. If it is open you have your smoking gun and you need to trace the circuit back through the wiring harness to the ignition switch to the ground attached to the switch which should ohm out short to the block also. Somewhere you will loose your ground.
 
The blk/yel wire is connected to the trigger signal emanating from the stator under the flywheel but physically connecting inside the CD module. It shorts out (to battery -, aka ground) the trigger such that the SCR that would normally conduct, shorting out the pulse capacitors and causing a spark to be delivered to the plugs, doesn't occur.
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Throw that dang Selco manual away..... when the key or kill switch is activated it sends the capacitor charge from stator to ground...nothing thru/from trigger.
 
faztbullet said:
Throw that dang Selco manual away..... when the key or kill switch is activated it sends the capacitor charge from stator to ground...nothing thru/from trigger.
Click to expand...

Well it surely doesn't make sense to me but I got out the ignition troubleshooting pages in the 60-125 HP serv. man. and it does make DVA high voltage checks for the "Switch Box Stop Circuit". Seems like a brute force method of killing ignition when other types of such in miscellaneous types of equipment, use a more subtle, low voltage, low power approach to stop a pulsed piece of equipment from firing.

I do apologize for the BS! Power wins again and rightfully so! Would be nice if the service manuals included schematics of circuitry for those who find them useful....yes we get wiring diagrams, but for "swappable units" it would be interesting. I suppose closely guarded OEM secrets might be at risk which could explain security of such. Doing nothing this AM, might just go to the CDM/CDI site and see if they have one posted. Any body reading this knowing of such would be interesting if you would take the time to post it. Do hope you get-r-fixed.

Edit: Well shucks, check this out: https://www.elprocus.com/capacitor-discharge-ignition-cdi-system-working/

Just as "The Man" said. Mighty simple circuit and apparently bullet proof since it has probably been used in millions of engines.

So Mr. Jim, you are still chasing the same problem in the same places, just a correction on what the kill circuit controls in the spark generation process.
 
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Some times it takes awhile. I'm out in the yard digging up a 4' deep x10' section of supply water line from the meter......by hand.

It just dawned on me the "why" ignition designers chose the part of the ignition circuit for stopping the engine they chose:

1. The charging pulses used to charge the ignition capacitors (the 100's of volts guys) are quick in duration and the average value is near zero. Fast pulses don't have time to establish fields (like a constant DC voltage does) that break down circuits and wiring and cause arcing and shorts in places not designed for such....like across the internal contacts of the ignition switch.

2. Running 3-20' or more of unterminated wire....the yellow/black kill wire from the engine to the control box, when the engine is supposed to be running, is actually a half dipole antenna that can/would pickup frequencies (pulses) in the engine ignition systems frequency band. To have that "noise" at the input to the ignition triggering device would surely/could play hell with the smooth running of any engine....no telling when you would get an ignition pulse/spark plug firing.

Hanging it off the ignition dump capacitors power input, at hundreds of volts, "noise" on the line would be negligible. Makes sense!
 
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