Re: 1984 Johnson 70 hp No Spark
Disconnect the large RED electrical plug at the engine.
Remove all spark plugs.
Rig a tester of some kind whereas you can set a spark gap of 7/16"... you could insert a #2 philips screwdriver tip into the spring connector that normally grips the spark plug, then hold the shank that approximate distance away from the powerhead.
Crank the engine by using a small jumper from the battery cable terminal of the starter solenoid to the small 3/8" nut terminal of the solenoid that engages the solenoid... NOT the ground 3/8" nut terminal.
If you have spark with that RED plug disconnected but no spark with it connected, replace the ignition switch.
Should you ever encounter a problem whereas the powerpack fails repeatedly, keep the following in mind.
Voltage To Powerpack Failures
(Magneto Capacitance Discharge Systems)
(J. Reeves)
The usual cause of having those type powerpacks fail repeatedly is having a very small of voltage applied to the Black/Yellow wire (Kill Circuit) at the pack. Test as follows.
Disconnect the Black/Yellow wire at the powerpack.
Insert either a ampere meter or a volt meter set to its lowest DC voltage reading between that Black Yellow wire and ground.
With the ignition key in the OFF position, observe the meter reading. Now turn the ignition key to the ON position and again observe the meter reading.
Any reading, movement of the meter needle, even a microvolt, would indicate that battery voltage is being applied to that Black/Yellow wire. If a reading is present, remove the other end of that Black/Yellow from the raised terminal of the ignition switch.
If the reading ceases to exist when the Black/Yellow wire is removed from the ignition switch, replace the switch. If the reading continues to exist, there would be a short of some kind in either the engine or instrument wiring harness.... to determine which, simply unplug the large RED electrical plug at the engine which would eliminate the instrument cable.
Note that the black/yellow wire must not have any other wire attached to it for the following reason!
Keep in mind that any accessory that has 12 volts running to it, especially when turned on, will have voltage flowing thru it and trailering out thru its black ground wire to complete the circuit. If that accessory has it's black ground wire attached to the "M" terminal that the black/yellow wire is attached to.... you will have voltage flowing directly to the powerpack.
