switch box help Merc 9.8HP

Rake1

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Joined
Apr 20, 2017
Messages
2
Merc model 110 9.8HP no points, I believe I am correct with the(110 model) have one of these and need some help serial # is 4243430 I believe it might be a 1975(please correct me if wrong) My problem was no spark, but now I have spark to one plug only,any ideas. Here is what I have done. Disconnected the ground off the kill switch, when I change the coils from one side to the other I then get spark on that coil so this tells me both coils are working. I am thinking switch box but am not sure how to test it.I did try my volt meter on the box and pull it over I get about 52 volts. Tried the other two for the other coil and only 0 to 7 volts so I assume the switch box is bad. But I do not know how to actually test it,any help would be appreciated. PS when I put the serial # into the search it says nothing found.
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Thanks guys
 

scout-j-m

Chief Petty Officer
Joined
Jul 31, 2009
Messages
601
I have a factory service manual and unfortunately it says use the "Thunderbolt Ignition Analyzer and to follow the instructions in the tester's manual".... so It's not too helpful there. Try looking up the troubleshooting chart on CDI Electronics' website. They should have some basic resistance readings to look for as well as some DVA specs if you happen to have a DVA attachment for your multimeter.

It could be that the trigger is faulty and not sending the fire signal to one cylinder. The manual says to disconnect the two brown wires from the trigger to the switchbox, and check the resistance between the two trigger side wire leads and look for a reading of 140-160 ohms.
 

Rake1

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Joined
Apr 20, 2017
Messages
2
No I just have the multimeter, I am not to good with the meter but did check the resistance on the two brown wires and got 144 but it was still connected when I did it. I will try that tomorrow with it disconnected. I would love to know how to test the stator and the switch box. would you have that info. I just assumed that because the switch box was only putting out power to only one coil that was the issue. Thanks for the help
 

scout-j-m

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Jul 31, 2009
Messages
601
I also sent you a message. Check the envelope icon beside your username at the top of the page.
 

scout-j-m

Chief Petty Officer
Joined
Jul 31, 2009
Messages
601
For the stator charging coils, the manual says to check "between yellow and white coil wires" looking for a reading of 750-1000 ohms.

In my experience of testing charging coils though, you are mainly looking for one not being totally shorted out and both coils to have similar readings even if they are out of spec.
 
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