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Mercury 50HP, 500SS will not shut off!

G

gdanderson

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I am waking-up a 1968 500SS, 50 HP Mercury Outboard (serial #2308167). Has been inactive for 10 years that I have owned it. Before that I suspect it sat for a least that long or longer. Have started motor in a barrel and it runs fine. However I ran it for a short period of time (30 seconds) as it did not pump water. Removed lower gear case and are in the middle of replacing impeller (it has a major set). To further test the motor with lower gear case still removed I reinstalled the water tube into the motor connected to a garden hose. Water flowed throughout the motor just fine. Started motor and ran great!!! However when I went to shut the motor down with the key in the MercControl the motor remained running. The motor turned over and started just fine. The starter acted just as one would expect. Moved the key from the off position to engage the started it worked as it should and the motor started. Releasing the key from the start position the key went to the run position and motor continued to run fine with the started disengaging from the flywheel. All normal! After I ran the motor for some 10 minuets I went to shut it off that when things went sideways. I moved the key to the off position and the motor continued to run. Moved the key back and forth from run to off to no avail. Finally pulled the choke to kill the motor. So....my question is where should I look for the problem. I have a standard MerControl that has been with this motor from day one.

Thanks for your thoughts
Greg Anderson
 
That motor should use an Ignition driver to power the switchbox - look at this diagram and see if it applies, if so to stop the motor the blue terminal is grounded in this case thru the orange wire.
1975-500small.jpg
 
OK this one is the one, note the white wire it provides +12v to the switchbox when running; to stop it the switch cuts the power.
650-500SS.jpgThere must be a short in the control or harness that is feeding 12v all the time.
 
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Well...I have it figured! On many of these old motors the wire color changes with time. Red morfs to pink, white turns to gray, orange goes to red ect. On this motor not only did some of the colors change the wire coating was severely cracked. I had to cut back and open up the engine harness to get to decent wire. In the harness was a salmon colored wire. I had assumed it was a red wire that changed to salmon color...wrong! Anyway i had extended a red wire onto the salmon wire and then went to the red terminal on the switch box. Once i changed the wire position to the correct location all is good.

Thank you all for your help.

Greg
 
Neither...I have a 500SS w/o Alternator. The closes diagram shown in this thread would be the 650SS and 500SS and that shows an Alternator. The color of wires shows different Alternator and NO Alternator.

Thanks again everyone

Greg
 
No the engine was built originally without an alternator. In 1968 it was a option. Yes the battery dose need to be recharged on occasion.
 
Please see Post #1 for serial #. Sorry I am not able to post photos. This site doesn't seem to want to let me Log IN with my phone that I have access to photos of the motor!!! The wiring diagram for my motor is: Merc 650S and 500S Breaker-Less Wiring Diagram with Ignition Driver.

Thank You
Greg
 
I don't think the stator ( alternator ) was an option on the SS ( solid state ) ignition models.----It would have come equipped with the stator for charging the battery.
 
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