Emergency Kill Switch Wiring

[ddrieck]

Hey all,
I am wanting to wire in an emergency kill switch on my 1986 Thompson Cutlass, same sorta kill switch like on PWC's. It has the 170 Mercruiser for powerplant. Can I wire the kill switch from chassis ground to the negative side of the coil to get the engine to die if the kill switch is pulled?

 

[Scott Danforth]

no, you wire in-line into the ignition wire (purple wire) back to the ignition.

there are two types of lanyard switches. the ones that close when you yank the lanyard. those are for magneto ignitions and you ground those out to kill. the other are for powered ignitions like you have, that open when you yank the lanyard, thus removing power from the ignition.

 

[ddrieck]

I did a test run on the boat a earlier this afternoon and run a jumper from chassis ground then touched it to the negative side of the coil and the engine died. So I wired the kill switch from ground to the negative side of the coil and the engine dies when I pull on the lanyard.

 

[alldodge]

I did a test run on the boat a earlier this afternoon and run a jumper from chassis ground then touched it to the negative side of the coil and the engine died. So I wired the kill switch from ground to the negative side of the coil and the engine dies when I pull on the lanyard.

While that does work, it should not be done on a 4 cycle motor. The kill switch should disconnect 12V to the coil (+ side), not ground the - side

As Scott mentioned you want to "break" the 12V connection, not "make" a ground connection.

Find the purple wire coming from the key switch and place kill in it, same as below

 

[Scott Danforth]

I did a test run on the boat a earlier this afternoon and run a jumper from chassis ground then touched it to the negative side of the coil and the engine died. So I wired the kill switch from ground to the negative side of the coil and the engine dies when I pull on the lanyard.

Your method is a coil flip if you just kill the motor and blow a fuse, or if you fry the wires in the harness

There are two types of MOB switches for a reason

 

[achris]

I did a test run on the boat a earlier this afternoon and run a jumper from chassis ground then touched it to the negative side of the coil and the engine died. So I wired the kill switch from ground to the negative side of the coil and the engine dies when I pull on the lanyard.

Then if you ever pull the cord and don't manage to turn the key off within a reasonable time, kiss your coil goodbye. It'll fry and die.

Do the job the right way (cut ignition feed, not ground the coil) or send it to someone who will. Half-fast jobs are what give the boating industry a bad wrap....

Chris.......

 

[nola mike]

Then if you ever pull the cord and don't manage to turn the key off within a reasonable time, kiss your coil goodbye. It'll fry and die.

And possibly other more expensive components in the ignition system.