No Spark on plugs unless this wire disconnected

[Michaelduf]

I have a 1972 Johnson 50 (50ESL72C).

I am having an issue with no spark on either spark plug. I figured out it is something to do with the key switch (which has a kill switch feature on it, so when you turn the key off it turns of spark to the plugs which shuts off motor). When I disconnect this black/yellow wire (top right in picture) from the power pack, I get spark back however now I can’t turn the motor off with turning the key to the off position. Wondering if this is a simple fix or if anyone can point me in the right direction.

 

[dingbat]

The key switch shorts the ignition to ground to kill the motor. Removing the wire circumvents this feature. If it’s not working with the key, you have something wrong in the switch circuit.

Put a meter on it to confirm, but I’m guessing your key switch needs replaced.

 

[racerone]

Post picture of the wiring harness , big plug on the motor.-----Both sides yellow ?

 

[Michaelduf]

Post picture of the wiring harness , big plug on the motor.-----Both sides yellow ?

Both sides red

 

[Michaelduf]

The key switch shorts the ignition to ground to kill the motor. Removing the wire circumvents this feature. If it’s not working with the key, you have something wrong in the switch circuit.

Put a meter on it to confirm, but I’m guessing your key switch needs replaced.

I will test with multi-meter. I’m hoping connection is loose and I don’t have to replace the switch as it costs over $100.

 

[F_R]

Both sides red

And therein lies the problem, I think. Without digging into the details, I think that motor requires a fairly unusual cable with yellow ends because it has both HydroElectric Shift and CD Ignition.

 

[racerone]

Correct ---this motor left the factory with yellow plugs.-----So it has been modified and who knows what was done.----Can not be of any help on this one.

 

[Michaelduf]

And therein lies the problem, I think. Without digging into the details, I think that motor requires a fairly unusual cable with yellow ends because it has both HydroElectric Shift and CD Ignition.

My bad. It does have yellow plugs. Not red.

 

[Michaelduf]

Correct ---this motor left the factory with yellow plugs.-----So it has been modified and who knows what was done.----Can not be of any help on this one.

My bad, it does have yellow plugs. Not red.

 

[racerone]

Wiring is easy to sort out in my opinion.

 

[Crosbyman]

not a 50 but likely similar..
see yellow-black and black on key switch (Ms) used to kill the motor when OFF

you need2 things ...
in OFF both M posts must show 0 ohms (dead short) between themselves !

secondly Y_Black must reach the engine side of the fat connector if you have one... make certain (M) BLACK is firmly grounded per picture or anywhere else ! clean all connections

check for end-end continuty of Y_B across the fat connector (check for corrosion) up to and including matching terminals !!

from https://maxrules.com/graphics/omc/wiring/1972_65_Eshift.jpg