converting a 1 motor kill switch to a 2 motor kill switch

[Popeye]

I want to install a product called an Autotether Wireless Lanyard in my boat. http://www.autotether.com/at/ I mostly want to be able to kill the kicker motor when I am trolling on Lake Michigan. I have a Tohatsu outboard for a kicker and Autotether does not have the correct clips to work on Tohatsu/Nissan outboards and has no plans to provide one anytime soon. Mercury makes a diode kit to connect 2 outboards to the throttle control kill switch but it's rather expensive. Since all the kill switch is, is a normally open switch and when tripped, grounds the motor ignition to it's frame, shutting it down.

I was thinking that if I wired the kill switch so that when tripped it would power a relay and would that would close two sets of contacts killing the motors (regardless which one was in operation). I had originally though about just running a parallel set of wires to the kicker from the switch but was told that would create problems with feedback from an on line motor to the off line one and could damage the coil/ignition sysytem.

So this is what I came up with. I'm sure I'm overengineering this.



If you want to recommend that I just install a set of wires and put in my own diodes, feel free to tell me the rating of the diode(s) I need because I don't have a clue.

[Reelsore]

Couldn't you just wire them in series?

[Popeye]

I was told that if one motor was in operation, there could be feed back to the off line one and damage the ingition system. Has to have a diode(s) to protect the other motor. Isuppose I could also just find out if a Yamaha kill switch would fit in the hole on my Tohatsu. and just use that. Mostly concerned about killing the kicker. I always wear the lanyard when driving the boat from the driver's seat.