Re: Does shorting out rectifier kill spark for 77 johnson 35 hp HELP!
The rectifier converts AC voltage being supplied by the alternator portion of the stator to DC voltage. It does not serve any other purpose and is not a part of the ignition circuit. Whether it is shorted completely or missing altogether, it should not interfere with the ignition (spark).
Spark test: Remove spark plugs, set up a tester whereas you can set a 7/16' gap for the spark to jump (the gap is important). Do not use the spark plugs to test the spark as that is a waste of time.
Crank engine over. If no spark, disconnect the black/yellow wire from the powerpack OR from the ignition switch, whichever is easier for you. Crank engine over again.... if you now have spark, either the ignition switch is faulty of a short exists in that black/yellow wire somewhere. If still no spark, the usual problem is a failed powerpack.
(Small Rectifier Test
(J. Reeves)
Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.
Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.
Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.
Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.
