Kills switch for a Mercruiser

Bachelordude

While im waiting for the replacement intake manifold to be installed I was wondering if I could install a kill switch on my Mercruiser. So I received the switch but originally I was thinking it would just tie into (in series) the 12 volt power side of the key switch so that when the lanyard was pulled it would kill power to the switch thus killing the motor. A friend who is a mechanic of sorts said it has to be wired in series to the positive side of the coil. Well on the kill switch it has 4 terminals, 2 marked with an "M" and 2 marked with a "C". "C: being coil. I checked continuity across the "C" terminals and no continuity with the lanyard attached which means with the lanyard attached there would be no power to the coil. This doesn't sound right? I do have continuity across the "M: terminals when attached. So do I just use the "M" terminals in series to the coil???
Thanks Much!!

Ian

C likely means common, does it switch between an M and a C terminal?  Not sure why it has to go to the coil, it can simply break the feed as you surmised from the switched side of the keyswitch.