They are what we call Dead mans, you put a flexiable cable around your wrist or to your life jactet and then a clip goes in the grooved slot to slightly lift the spring loaded plunger and so dis the earth connection. If you get thrown out of the boat the clips is pilled out and the engines stop. Usually used on Outboat engine boats but also on I/O on small boats up to about 30ft. The problem espacailly with single engine outboard boats is, if you let go of the steering ie thrown out the rotational torque of the engine will turn the engine to one side normally the right and continue to turn in on a decreasing circle, normally to where you where thrown out and then ouch and your fish food!!!!!!

Sean

Don't they disengage the gears and keep them in neutral so you can rev the engines? My disengage buttons are square and on top of my shifters.

Maybe they're buttons to allow the outdrives to be raised above the "trim" range, into the "trailer" position ? Some VPs had that facility, the trim button pressed on it's own would only take the outdrives up so much, then both had to be pressed. (the electronic trim control unit/ trim senders on the outdrives with 3 wires, not the more common 2). Mercruisers have "trim" and "trailer" set ups also.

Graham

Thanks for the ideas guys.

I need to double check, but when I tried to start my port engine with the broken switch removed the starter cranked, but the engine didn't start. Manually completing the circuit allowed the engine to start right up. I highly doubt this was coincidental. The wires trace to the wire harness for the trim controls and shift engage bypass stuff.

Maybe the just added a few "extra buttons" to make the helm "look cool"? LOL