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Old 22 September 2019, 19:01   #1
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79 Mercury 402 high idle

Hi I'm new here so wanted to see if anyone knows how to properly time a 78 Mercury 402 40 hp? Another forum told me not to worry about timing marks and to justturn the screw back. I verified tdc and found the spec 5-7 degrees before. Ran the engine unhooked the neutral warm up cable so I could adjust the turnbuckle on my trigger to match the timing mark and now it is still at 1800 rpms and hitting on the dot. What's going on!
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Old 26 September 2019, 17:20   #2
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Motor has been experiencing high idle rpm before ? Why do you think the timing is not set right, has someone been fingering the motor ? if not, just adjust the idle screw some CCW turns till idle lowers to its factory specs.

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Old 26 September 2019, 17:51   #3
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Thanks for response. Shop had it running right nice and smooth.new fuel pump, water pump, carb rebuild, Lync and sync, and it ran good for a couple days. Few days later, it wouldn't start for anything. Took it to a merc certified mechanic and the dva readings were bad and had weak spark. He told me to get a switchbox. I got a switchbox put it on, still hard to start. I investigated and found the kill wire had two volts so I unhooked it and it fired up. But it was idling super high so I stuck a timing light on and it was at like 20 after tdc so I adjusted it back to 6 before tdc which the book says and still idled at 1800. Idled high no matter we're it's at.
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Old 03 October 2019, 17:08   #4
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Is the timing advance and the carb synch independent from each other or the timing is synched directly to the carb ? The motor is a tiller or a central console model ? Have you tried moving the vertical idle screw some turns backwards to decrease the high idle ?

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Old 03 October 2019, 19:42   #5
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Attached a picture turnbuckle style adjustment
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