Hello all.

I'm getting on slowly with getting the little BMB engine from this thread in the boat and running:
viewtopic.php?f=6&t=8997&p=25670#p25670

Most of the installation is done, I'll update the thread when I have some images, and the engine is timed up and giving a good healthy spark on both pots.
All it needs is some fuel and it should run, although I will need to sort out some cooling to run it for more than a few seconds.

And that's where I have a problem, there is no provision at all on the engine to stop it once it's running.
I can pull the plug leads off of course, but can't do this when it's in the boat.

Can anyone suggest what I can do with a simple switch to earth to kill the sparks based on the images below?
ie, what should I earth?

Thanks

Nasher