Motor won't shut off????

[marxsman]

I have a 1965-66 Mercury 500 series 50 hp outboard motor and I bought it for cheap. Did all the maintance and the motor runs like NEW but it won't shut off. Turned the key off (electric start works)...still running.....unhooked the harness to the motor..still running. I had to un hook the fuel to get the motor off. What is the deal and is it missing something.

 

[marxsman]

Re: Motor won't shut off????

OK, I still need input please. I am new at this. I did get a wiring diagram and noticed that the starter cylinoid was wired wrong. I switched the wires but have not pulled the boat out to start it. could that have been the problem? I did check and the starter still works but I won't know if it shuts off. Also this motor does not have a switch box and the diagram shows none either. BUT the mercury kill switch is missing but the motor still runs great.

 

[thefairlaneman]

Re: Motor won't shut off????

If it has a magneto (my 1960 model does) you ground out the magneto with a kill switch wired directly to ground. works the same way the kill switch does on a lawn mower.

 

[monk-monk]

Re: Motor won't shut off????

i've been thinking about this marxsman...i wanted to reply earlier but really don't know that ignition system. it could have been the way the solenoid was wired...seeing how you say it has no ignition box...something is allowing the ignition source from the magneto to continue to supply voltage to the coil which then sends that voltage to the spark plugs...thats why when you disconnected the wiring harness, it didn't stop the motor...somehow the ignition circuit is staying closed, or not grounding out the magneto to kill the spark and the magneto will continue to feed voltage to the coil even if theres no battery hooked up...thats why when you disconnected the wiring harness it never stopped the motor. the ignition circuit is not being broken or the magneto is not getting grounded out. just my opinion...i could be wrong!

 

[marxsman]

Re: Motor won't shut off????

This is driving me crazy. You are right, I know the magneto is not grounding to shut off the motor but now we figured that out I have NO idea how to wire a kill switch. Also, shouldn't there already be a kill switch installed somewhere on the motor?

 

[monk-monk]

Re: Motor won't shut off????

i believe the only way to "kill" the voltage from the Mag is to ground it out...as one person replied, with an old lawnmower, you used to literally press a ground lever against the end of the spark plug to kill the voltage...but you have a "keyed" ignition system so i would think that by "turning the key" to the off position it would then ground out the Mag...CHECK that ignition switch to see if its grounding that Mag...if you have a key to start it, then the key should kill it...no getting up to go ground it out...the key should be grounding the spark..

 

[marxsman]

Re: Motor won't shut off????

I initionally thought that was the problem but I turned to key off and the motor still ran....then I unplugged the harness and that did not shut it off. SO my only conclusion was that there is a wire missing or not hooked up right. The manuel is being shipped so dont have that until Tues. I just figured there is an ignition kill "something" somewhere is the motor housing. OR just thought of this. Is the ignition kill I'm looking for "the key" switch and this is not grounding properly? therefore not shutting the motor off?

 

[monk-monk]

Re: Motor won't shut off????

thats what im saying, that "keyed" switch that starts the motor should also kill the motor...it sounds like the key is not grounding the Mag...be it a bad switch or the wire on the other end not grounding out the Mag...when you turn that key to off, it should be grounding out the Mag...

 

[marxsman]

Re: Motor won't shut off????

I got ya. sorry it took so long for me to understand.. I'll try that in the morning and let you know.

THANKS, THANKS and Thanks

 

[marxsman]

Re: Motor won't shut off????

just an update. I replaced all the wires in the ignition, new wires etc. The ignition still did not shut the motor off. So, I ended up running a kill switch all the way up to the control box with an external switch. It now works and shuts the motor off. I did this by running a wire off the positive feed from the magneto to one side of the switch and the other to ground.
Flip the switch and kill the motor.