wrote

I don't really want to get between Larry and an electrical problem but
I did once know a bloke that had a built in tube, in the transom,
where he stored his MOB pole. It apparently had a mercury switch built

And Terry,

I had that thought and, environment aside, it is probably what I would do
except that the pole has to be stored in a vertical positon on my boat.
Even if I felt like cutting up the boat for a stern tube, the pole would
extend into the main cabin.

The reason I want something flush is to minimize things that can snag. The
line to the horseshoe lifering will be in the water with the PIW's feet so
the less projections, the better. I also wouldn't want the light to get
kicked off accidentally by being kicked.

Something like a jetski kill switch might work but the elegant thing about
the magnetic reed switch is that a pull on the Velcor strap in any direction
will strip off the magnet. If the lanyard has to pull straight out to
activate the switch, it's going to be hard to rig so it works reliably. I
don't want the person releasing the pole to have to remember to turn it on
in the heat of the moment.

--
Roger Long