Engine won't shut down with key

[seachest]

Recently had quite a bit of work done on my OMC Sea Drive including replacing the powerhead. All had been working fine then out of the blue, I can turn off the key and remove it but the motor still runs. The only way I can get it to shut down is to either break the connection in the wiring harness inside the cowling which I might add is not very convenient, or to push in the fuel enrichment (choke ??) on the ignition switch and hold it in until the motor dies. I'm beside myself and looking for answers as to how this could develop out of nowhere. I have replaced the ignition switch and the problem persists. I did notice also that my batteries drain prematurely and that there is a pigtail coming off of the black magneto negative wire and the purple ignition wire neither of which are connected to anything. Should they be connected to each other? Although they don't look like they've ever been connected to anything, I guess it's possible that they had been cut intentionally.

Please, any and all possible solutions are welcomed

B_Dub l u

 

[UncleWillie]

Some ignitions are powered from two sources.

The ignition key sources a reduced power supply through the ballast resistor while the key is ON and the engine is running.
The second source comes from the starting solenoid and delivers full power only while the starter is engaged.
If the wire from the coil to the starter is on the wrong connection it may be supplying power 100% of the time, even with the Key OFF.
This will drain your battery if the engine happens to come to a stop with the points closed.

Measure the voltage on the coil with the Key OFF. If you see power, that's the problem.

 

[seachest]

Thanks Uncle Willie for your quick response, Unfortunately for me, I'm not sure I understand it so perhaps some additional information from me will help.
This is an older OMC Sea Drive. 4 Cyl outboard. There are four individual coils on this motor. No points, ballast resistor, etc that I am aware of. Therein lies my confusion with your response.

 

[UncleWillie]

I am not familiar with that particular engine.
In re-reading the opening post I missed where you mentioned Magnetos.

To shut down a Magneto engine you need to ground the magnetos.
The terminal marked "M" on the key switch does this.
The "Ground is provided by another terminal on the Key Switch label "MG", "G" or "M". (2nd "M").
If this isn't grounded the engine keeps running.

With the Key OFF, you should measure a ground on the "M" terminal.

What size engine is it?
Electric start?

This might help. See diagrams E thru H.

 

[seachest]

Yes OMC Sea Drive 1.8 Litre 140HP Electric start - Thanks once again for your response and expertise. I will have to trace the M Ground wire back and see if it is broken or simply dislodged And thank you for the link to the diagrams - I will keep you posted ,, The best to you Uncle Willie !

B Dub L U

 

[seachest]

To Uncle Willie - Your advice led me in the right direction, sir. I found that the magneto ground pin in the main wiring harness had become displaced. It was pushed back into the harness housing and wasn't making connection. The harness plugs are a wee bit mushy from age so if they are not properly aligned when trying to connect them they will move, Thank you again for the leads and diagrams. The problem is now solved !