# How Does a Kill Switch Work?



## NKlamerus

An anyone give me a short synopsis in English how a marine kill switch works? 

I'm working on a 1998 Sunbird Fish and Skii. The previous owners (my drunk uncle) removed the kill switch some time ago. 

Looks like only 2 wires were cut? 

Does it short out the ignition switch? Or is it an ohm rating?


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## rustybucket

In our last boat it interrupted the ignition wire from the key switch to the engine. 

Not sure if this is standard or not, but about made me start ripping out wires when the kill switch on our old boat went bad and left the circuit open even when the dongle was inserted.


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## SteveCal

Automotive class 1960. :whistling:

Kill Switch: Grounds the power from the coil or magneto to the block.

Ignition Switch: Close switch (On) Power passes thru to points, coil, etc.. Open switch (Off) No power flows thru the switch.

Example: While flying a Powered Parachute at 1000 AGL do not mistake the magneto kill (ground) switch for light switch.:no::no::no: Because engine becomes deafeningly silent and lights do not come on.:001_huh:


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## NKlamerus

So it is a ground. Do they typically avoid any connection with the ignition switch? 

So, if the kill switch is off/pulled, the engine will crank with no Spark. Correct?


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## sealark

The kill switc is usually incorperated in the switch as a slip in with a lanyard on it attached to the driver. If he falls overboard the switch kills the engine. By grouunding the switch. Just like turning the switch further to off. If it has a push pull switch it has been jurey rigged. And has a push button to start engine. Inboards are similar but never seen a lanyard pull out on inboard. But high speed might have them.


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## NKlamerus

I understand the purpose I just don't know how it was wired in. The wiring for this boat is crazy.


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## SteveCal

NKlamerus said:


> I understand the purpose I just don't know how it was wired in. The wiring for this boat is crazy.


Very basically. 
Ignition switch. A heavy wire will come from a power source (Battery/distribution board) to the ignition switch. When in off position no power is distributed from the switch. In start position power is sent down one wire to the starter solenoid. In the run position power is sent to the coil, light switch and accessories.

Kill switch. A wire will run from the magneto to the switch and from the switch to the engine block. As long as the switch is open (on) the engine runs. Close the switch (off) and you are effectively grounding the magneto to spark plug wire to the engine block. A magneto produces its own power to the spark plugs. 

Where are you located?


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## NKlamerus

SteveCal said:


> Very basically.
> Ignition switch. A heavy wire will come from a power source (Battery/distribution board) to the ignition switch. When in off position no power is distributed from the switch. In start position power is sent down one wire to the starter solenoid. In the run position power is sent to the coil, light switch and accessories.
> 
> Kill switch. A wire will run from the magneto to the switch and from the switch to the engine block. As long as the switch is open (on) the engine runs. Close the switch (off) and you are effectively grounding the magneto to spark plug wire to the engine block. A magneto produces its own power to the spark plugs.
> 
> Where are you located?


That is absolutely perfect. I'm going to trace the wire from the Magento to the console. Unfortunately this boat had factory harness' and every few feet there are plastic clip connections. 

I can see the wires they cut, I believe it was 2 black/whiteline. Can't remember off the top of my head. 

I am located in Valparaiso. 

I'm am fairly mechanically inclined, ive pulled and built many motors, but only one other outboard. (Merc 150 Saltwater)


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## submariner

the answer to your question, the starter will turn but the engine will not start.


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## SteveCal

NKlamerus said:


> That is absolutely perfect. I'm going to trace the wire from the Magento to the console. Unfortunately this boat had factory harness' and every few feet there are plastic clip connections.
> 
> I can see the wires they cut, I believe it was 2 black/whiteline. Can't remember off the top of my head.
> 
> I am located in Valparaiso.
> 
> I'm am fairly mechanically inclined, ive pulled and built many motors, but only one other outboard. (Merc 150 Saltwater)


Yeah. You'd think wiring on a boat would be a simple thing. I have run across some real rats nests. And Old Unkle Fred, the know all - do all of the "cut-em and twist-em together" shop were electricians tape is king can really ruin a good day.


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## SteveCal

Have you done any more work on the wiring?


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## NKlamerus

SteveCal said:


> Have you done any more work on the wiring?


Yeah, all new switches, new panels, new grounds everywhere, I also added a 12v. plug.

I find it odd the 1 ground wire was 16 gauge and everything else is 12 gauge. 

I still haven't tried cranking the motor again, ive got spark plug tester (Which will tell me if there is power to the plug), if there is; there shouldn't be an issue with the kill switch removed. Correct?

Pulled the windows and wet sanded everything tonight.


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## submariner

Never saw a sparkplug tester We just used to pull one plug and hold the tip to ground while someone else cranked the engine over ? if you saw a spark, was good to go almost forgot, we also looked at the color of the spark, weak spark, bad coil.


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## SteveCal

If it uses a kill switch you will not be able to turn the engine off once it starts. The mag kill switch 'grounds' the mag to.....well.....ground. Thats what kills the engine.


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## Hydro Therapy 2

the kill switch will either go open or ground out.


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## NKlamerus

submariner said:


> Never saw a sparkplug tester We just used to pull one plug and hold the tip to ground while someone else cranked the engine over ? if you saw a spark, was good to go almost forgot, we also looked at the color of the spark, weak spark, bad coil.


Yeah we still do that on the lawn mowers, my father bought one for a Vortec Issue. It was easier to buy one then hold one over the fan and belt.


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## NKlamerus

SteveCal said:


> If it uses a kill switch you will not be able to turn the engine off once it starts. The mag kill switch 'grounds' the mag to.....well.....ground. Thats what kills the engine.


Not the key? Off-Run-Start, turning it to off won't kill it...?


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## SteveCal

NKlamerus said:


> Not the key? Off-Run-Start, turning it to off won't kill it...?


If the mag kill wire goes from the mag to the "off" side of the switch and continues to ground it will kill the engine. That is how it works. Read the circuit and see what you come up with. Or if that is the switch it came with and the ignition switch wire loom wasn't messed with give it a try.

Edit:
Wait a minute. You said your drunk uncle cut the two wires to the kill switch. How was he killing the engine after that? Or did he?


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## NKlamerus

SteveCal said:


> If the mag kill wire goes from the mag to the "off" side of the switch and continues to ground it will kill the engine. That is how it works. Read the circuit and see what you come up with. Or if that is the switch it came with and the ignition switch wire loom wasn't messed with give it a try.
> 
> Edit:
> Wait a minute. You said your drunk uncle cut the two wires to the kill switch. How was he killing the engine after that? Or did he?


I'm assuming the key still cut the engine. 

Unfortunately, I can't get ahold of him. Texts, calls, and messenger don't work to find out if there were any issues. 

It was actually my step grandfather's boat, and when he moved he gifted it to me for free. I just had to put a new axle on it. 

The engine has had work done but I'm not sure what, it is extremely clean. And looks very well maintained surprisingly. The tank has been pickled and the mechanic winterized the system. (Whatever that includes, im assuming some kind of protectant in the cylinders and draining the hoses) 

I may start a build thread, just not sure how interested how everyone would be


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## kanaka

SteveCal said:


> If the mag kill wire goes from the mag to the "off" side of the switch and continues to ground it will kill the engine. That is how it works. Read the circuit and see what you come up with. Or if that is the switch it came with and the ignition switch wire loom wasn't messed with give it a try.
> 
> Edit:
> Wait a minute. You said your drunk uncle cut the two wires to the kill switch. How was he killing the engine after that? Or did he?


The kill switch kills the spark while the key switch is still in the run position. Kill the engine normally by turning the key to off.

If you're still unsure of how the kill switch is working, switch your multimeter to continuity, place leads on the terminals, put the clip in and yank it out. That'll tell you if it's open or closed when the clip is in place.


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## SteveCal

I shoulda come over and help you with the boat rather than wasting all day at the beach and on the T-Pier. Would have accomplished more and not got an ear ache. LOL.


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## NKlamerus

SteveCal said:


> I shoulda come over and help you with the boat rather than wasting all day at the beach and on the T-Pier. Would have accomplished more and not got an ear ache. LOL.


You in valp?


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## SteveCal

Mossy Head


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## NKlamerus

SteveCal said:


> Mossy Head


Ah, but you were at the T-Pier in Valpariso eh? Any luck?


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## BillyJ

Ok, help me to understand, I have an older 1978 Chrysler 8 HP motor (82H8J). There are two un-connected black wires running to an empty hole beside the choke (something missing from the hole). If they are connected, does that keep a circuit open for the motor to run or does it ground out the coils and stop the motor from running? I understand that some need the wires connected for the motor to run and some need the wires connected to kill the fire, something about whether you have magnetos or coils...

Thanks, Bill


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## JoeyWelch

You wear it.
Or you get Killt.

That’s how it works.


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## BillyJ

This is what I am referring to above in my earlier post:

"Spark is one of the main requirements for an engine to run. The older motors will have a Magneto type ignition. In these, spark is generated by the flywheel magnets rotating around a coil of some sort. Motors newer than about 1978 (depending on manufacturer and model) moved onto electronic ignition, eliminating the points, using a new Capacitor Discharge system and a power-pack."

Would the two black wires I mentioned above supposed to be connected to something like an off/on switch (not a "kill switch") that connects a circuit or breaks a connection?

* (there's an empty hole beside the choke where the two un-connected black wires run to) 

Thanks, Bill


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## kanaka

Start the motor, connect the black wires to each other and see what happens. 
If the motor won't start in the first place, connect the wires together. Then while it's running, disconnect.


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## BillyJ

If it runs with the wires connected, then it's an off/on button (switch) missing, right Kanaka?

Bill...


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## Boatfly

This is what not using a kill switch does, boat kills.
http://www.nwfdailynews.com/news/20180625/pc-boater-struck-by-own-boat-dies-of-injuries


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## BillyJ

From what I have learned, a regular "Kill Switch" that comes from the factory installed will kill the motor, period, and is used to stop the motor. However, if you are alone and ejected from the boat, they are useless, there's nobody to activate it in the boat.

What Boatfly is referring to above is an "Emergency Kill Switch" kit which you have to install yourself. It has a cord that is attached to the driver and will instantly kill the motor if he/she is ejected from the boat.

BillyJ


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## kanaka

The "kill switch" you are referring to is the ignition switch, off, run, start. The "emergency kill switch" usually is usually installed at the factory.
In your case, sounds like it broke and a replacement was never installed.

Example:


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