I just purchased a billet kill switch from E .C.M. for twins and it has 6 total wires, 2 purple, 2 purple with stripes, 2 black. The black wires do not make sense to me. I assume that the switch needs grounding, but why?

the older style emrc igition kilss would ground the igniton out.
same with outboards.
either these are old or they are universal to work with both.

Monstaaa is correct, they are set up to be universal, it will work for any application I/O and outboard.

Sounds like it's a universal setup. Black would not be needed on yours. I just installed one yesterday. You splice into the purple ignition wire and install the switch. The switch acts as a simple circuit. Lanyard attached allows power to the coil or MSD box. Lanyard off breaks the circuit killing 12v to the coil or MSD Box depending on how you have it wired.

If using a MSD ignition box (hoping you do), see the link for the instruction manual PDF. Page 5-6 is wiring. Ground either the violet or white depending upon your MSD set-up and you have your ignition kill. Easy Peesy.
http://www.msdignition.com/pdf/6460_frm23105.pdf

Thanks for the replies, your right about the ground not being necessary for me. E.C.M. said that the 496's use the ground. Got it done, can't believe wasn't one standard on the boat. Eric

So can I just inline connect to re or black, I have no purple

I'd use a multimeter and verify, but I assume purple/purpleStripe are the in/out.

You can ignore the other wire. Cutting the power wire to 'run' on mine kills the engines... unless said engine has a bad alternator in which case it stays running anyway! but that's another story.

I have no purple, my colors are red, black, Tan, Yellow, White and two browns

Ayuh,.... This is why you shouldn't hy-jack a 12 year old thread,.....

Whatcha workin' on,..??