238V out of magneto ground ignition switch pin

[tmetals]

1999
bayliner capri 1800 bow rider
mercury force 120 outboard

long story short.

none of the factory gauges or switches were working in my boat. i ordered new gauges and led latching as well as momentary 5 pin switches and some bosh 5 pin relays,

i fired up the boat after sitting through the winter. everything seemed as it was when it was parked last year.
i traced all wires, and labeled them individually. i ran through the bayliner owners manual wiring diagram, as well as the mercury wiring and made sure things made some sense to me. once i felt i had a grasp on what i was doing i replaced the factory 2 pos switches with the puch button. then i did the gauges.
now here is where things became weird.

i removed the factory 6 pin ignition switch. replaced it with a 2 installed a latching 5 pin switch for the choke, a momentary 5 pin for start , hooked up to a bosh style relay.

it took me about 4 hrs but i got everything to work in series.
untill i tied it all together with a new fuse block.

the boat cranked all day long but would not fire. turns out the ground and the magneto ground are not the same "GROUND"
and they technically work as a switch together when the key is off and on.

just for ease i un-hooked the magneto ground BK-Y wire from the fuse block and let it hang.....the boat fired up right away, but would not turn off at the key.

i tested the voltage from the magneto ground BK-Y, and i am receiving 240V from the magneto ground wire. when i hooked up the original 6 pin ignition switch, everything works as it should. on/off, start/stop, choke.....
but when the motor is running and at idle, when i test the back pin on the magneto ground it is reading 238-240V. this seems like a massive amount of power flowing through some 16ga wire and a switch.

does anyone know what the voltage should be at the ignition switch with the boat running?

i have been on this for over a week, and our annual 10 day dessert lake trip is two working days away and i am running out of options and sleep.

does this seem like a safe amount of voltage to be hooked up in a 12v fiberglass boat?

I am aware the magneto generates power. up to 20,000V , but is it normal to have this kind of power at the back of a dash switch?????

please help...

thanks

 

[GA_Boater]

Welcome aboard.

With the motor running touch that wire. You will get the shock of your life and this is normal on a magneto system. The wire is open when the stop switch/ignition switch is in run or start, so there is no completed circuit until the stop/ignition switch is turned to off when a ground is connected to kill the magneto.

With the key/switch on and motor not running, what is measured on the disconnected wire and what is measured on the fuse block connection you're connecting it to?

 

[tmetals]

Thanks for the reply,
I did manage to ground myself out last night as I was insuring the meter into the wire.
Didn't feel so good.

I have gotten mixed opinion's on this situation from mercury dealers in the Seattle area.
I did find a service manual for a mercury 10hp that stated the current load of the magneto ground is 400VDC and the idle range was 180-300 VDC give or take depending on my memory.
But at 240v I was in range.
Ilit is just very supra sing to see those amps out of a 16ga wire. I have not measured the amps but I imagine they are low.

I am working with the mercury dealer service's and just double checking those numbers are correct. .

 

[GA_Boater]

As I said - The high voltage is normal and nothing to worry about even on 16 gauge wire. You mis-wired something if it was working before because ground is applied to the magneto to shut the motor off.

Did you check what is on the fuse block connection you connect the wire to?

 

[tmetals]

You are correct on the wiring.
I was able to start the boat but not shut it off when it was running.
I had to use the kill switch,
I did check volts with power off and ignition off. And I am getting nothing, and that appears normal because the magneto ground and the ground are acting like a switch to kill power , as I see it
As far as the fuse block....
I am not sure about that, as the magneto wire is running aft forward and only the ignition ground idls going to the ground.
I will poke around and see if I can find a loop from the fuse block running back aft to the motor