Kill switch

[mark24]

Hi, I want to install a kill switch on old iron (Merc KG-7). I imagine that I should run 1 wire from each set of points. The 2 wire switch will act to connect the 2 sets of points together preventing any switching. Correct?

[JP53-N]

Correct

[bh/]

Not in all cases, and I do not quite understand why.
We sent a M20H out to race last month, started normally, went up on plane, but ran ratty. Driver noticed kill switch not plugged in, did so, and it ran smooth.
Some how those Phelon mags, when linked together, or linked to a common ground [same thing], will still fire.
Most do not, and you will kill both sides by grounding the points.
Any one with insights on this?

[sam]

If one set of points is weak, it will give the problem

[T Chance]

In my opinion it is best to use a 3-wire kill switch. One hot from each coil and a ground.

[trident]

3 Wire Kill Switch

But, be aware that some 3 wire kill switches are equipped with one lead common, one lead normally open, one lead normally closed, so that they work on various ignitions which may need the circuit grounded or opened to kill the motor.

Jerry

[bh/]

In my opinion it is best to use a 3-wire kill switch. One hot from each coil and a ground.

Tim; -a 'ground' to what ?
-if you ground to the block, then all you are doing is connecting the two sets of points.
This is where the problem crops up with the poppers.
I never saw this until recently.
Any KG4/7 I had worked fine grounded together?

[Mike45]

The trick is getting the correct kill switch for these motors and do not let the spliced ends in anyway get wet this will ground it out. And if you splice it and black tape it and stagger the connections. I just had some trouble 2 weeks ago with the ends getting wet and the motor started "stuttering". Once I mounted the wires up I had no problems. But like I said not all kill switches will work on these types of ignitions. Don't ask which kind to buy from me I just buy the one with a 4 prong hook up and find which two work and this also lets me use different types of motors.

[jeff55v]

For your amusement.

When I was a kid, my Dad was always on a shoestring racing budget. Once he rigged up a kill switch for me on my J runabout. He used a standard set of used breaker points, ran a wire from each of the motor’s points to it. Then stuck a piece of plastic with a lanyard tether between the “kill switches” contacts. When I pulled the plastic from the contacts, it grounded the two sets of points together. It worked ok, except it was too easy to accidentally pull the kill switch. After a couple races lost on account of his kill switch, he was able to come up with a store bought kill switch.


Your local Napa auto parts store can get you decent kill switches thru Sierra. You can look up the switch part numbers and photos online.
I hope this helps.

[champhotrod]

More confusion

Also be aware that some of the Bendix ignitions used on Mercs have the points open at the same time during a revolution and one won't ground the other!

Cooper

[sam]

Cooper can you explain that? I thought the point opening depended on the cam ground on the crank and all the cranks are the same, aren't they?

[ram95]

Maybe he's referring to Mercury's "phase maker" ignition system (I call it spark for the 3rd world community) as found on the infamous Merc 75. I think Elmer must have taken great pleasure in personally firing that engineer. That kind of warped imagination and creativity, as it were... had no place in an outboard motor. Probably came from British Leyland or BSA/Triumph Coventry as they were collapsing.

[champhotrod]

Bendix

Cooper can you explain that? I thought the point opening depended on the cam ground on the crank and all the cranks are the same, aren't they?

Sam,
On the Kg7 type engines there is no cam ground into the crank, for the Phelon type ignition a small removable cam slides over the top of the crank. The Bendix ignitions have the cam on the magnetic rotor or even earlier versions have the cam on the inside of the flywheel. Certain Bendix Scintilla rotors have the cam such that when one point is open while the other is opening so that connecting the two together does not ground them.

Cooper

[T Chance]

Tim; -a 'ground' to what ?
-if you ground to the block, then all you are doing is connecting the two sets of points.
This is where the problem crops up with the poppers.
I never saw this until recently.
Any KG4/7 I had worked fine grounded together?

Yes it connects two sets of points. But the 3rd wire that runs back to the block, head, crankcase or whatever grounds both of them out. This is the type of switch that Konig used for years. It is similar to the common fishing motor switch with four connectors with the choice of using one set of two to make a circuit or the other set that will break a circuit except it has three connectors and will only make a circuit.

[bh/]

Yes it connects two sets of points. But the 3rd wire that runs back to the block, head, crankcase or whatever grounds both of them out. This is the type of switch that Konig used for years..

-a light is beginning to flicker........
I think the popper that won't shut down is two wires ,
ie; one each from the coil side of the points, forward to an open/close switch. So all we are doing is connecting the points to each other, not to ground, and this is not working on this motor, but does on some?
Taking each wire forward to two poles on an open switch,
then connecting them together thru the closed switch, and to a 3rd pole back to ground on the motor,
ie; a three wire system, connects the two points and grounds them out. That will kill the ignition.
Strange though, that both 102s I have here use only
the two wire system, ie; connecting points to each
other, but not to ground, and works consistently ?