1986 Merc 75HP serial# 0A995041 won’t shut off

Raltex26

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Aug 24, 2022
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I recently purchased a 1986 Merc 75HP 4 cyl serial# 0A995041 ELPTO (model# 1075726 I believe)
My issue with it is it won’t shut off. It’s on a stand and it has quicksilver controls and it won’t turn off with the key, sometimes the engine seems to change sound and lower rpm a little when I turn off the key but it doesn’t kill the engine. Is there some wires I need to check? Or is it dieseling?

I recently went through the carbs with cleaner and installed new needle and seats and gasket kits, and a diaphragm and gasket kit for the fuel pump.

I set the mixture screws to 1.5 turns out and guessed on the idle. It runs pretty good I need to lake test it but the darn thing won’t shut off.
 

Raltex26

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Aug 24, 2022
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I followed it and checked continuity all around and it does go to ground but I’m wondering where in the round plug or how does the key ground it. Like how do I test if the off position of the key is grounding that wire
 

Raltex26

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The back of the ignition switch has all terminals with something terminated on them.

Also the “run/off” switch to the right of the throttle handle doesn’t seem to effect the engine either
 

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Raltex26

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Here are some more photos
 

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Raltex26

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The other thing I did was jumper the black and yellow wire to ground from the switch box where the black and yellow was terminated and jumped that to ground and the engine kept running.
 

racerone

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Dec 28, 2013
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38,051
There is an issue with the kill circuit.-----Black / yellow stripe wire.-----I can not see your boat.----Up to you to dig into this.
 

Raltex26

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Aug 24, 2022
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Thanks for the response Racerone, I completely checked everything the kill circuit is completely working as it should. However I looked up the CDI switchbox that’s in it and it is the CHEAPEST one on Amazon. Could a faulty switchbox keep you from being able to turn off the engine?
 
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