79 Mercury OB switchbox vs. rectifier.

[Nohfire53]

I have a 90 HP L6 Mercury with no spark. I have tested the switchbox and I get no spark from Tue coil wire. Some individuals have eluded to it not being the switchbox but the rectifier, as I consult Dr. Manual Seloc, it doesn't seem like the stand alone 3 post rectifier has anything to do with the ignition system and only has to do with the charging system.
Is that true?
Does the switchbox have a built-in rectifier? It does convert/invert volts somewhere.

 

[Maxz695]

Re: 79 Mercury OB switchbox vs. rectifier.

Sending test for 40 hp 4 stroke should be the same will be on next post

 

[Maxz695]

Re: 79 Mercury OB switchbox vs. rectifier.

Rectifier Test
WARNING
Disconnect battery leads from battery before
testing rectifier.
1. To gain access to rectifier, remove 6 bolts from
electrical box cover and remove cover.
54645
b
a
a - Bolts
b - Cover
NOTE: Rectifier can be tested without removing from
engine.
2. Disconnect all wires from terminals on rectifier.
3. Use an ohmmeter (R x 1000 scale) and perform
the following test.
07300
d
a
b
c
f
e
a - Terminal
b - Terminal
c - Terminal
d - Alternator Terminals
e - Positive Terminal
f - Ground
Connect red meter lead to ground, black lead alternately
to terminals ?a? and ?c?.
Continuity Indicated.
Connect black meter lead to ground, red lead alternately
to terminals ?a? and ?c?.
No Continuity Indicated.
Connect black meter lead to terminal ?b?, red
lead alternately to terminals ?a? and ?c?.
Continuity Indicated.
Connect red meter lead to terminal ?b?, black
lead alternately to terminals ?a? and ?c?.
No Continuity Indicated.
Rectifier tests O.K.
No Continuity Indicated.
Connect black meter lead to ground, red lead alternately
to terminals ?a? and ?c?.
No Continuity Indicated.
Replace rectifier.
Continuity Indicated.
Connect black meter lead to terminal ?b?, red
lead alternately to terminals ?a? and ?c?.
No Continuity Indicated.
Connect red meter lead to terminal ?b?, black
lead alternately to terminals ?a? and ?c?.
Continuity Indicated.
Replace rectifier.
Continuity Indicated.
Rectifier tests O.K.
Continuity Indicated.
Replace rectifier.
No Continuity Indicated.
Replace rectifier.
No Continuity Indicated.
Replace rectifier.
Continuity Indicated.
Replace rectifier. single pole lower is B top left is A and top right is C terminal

 

[Faztbullet]

Re: 79 Mercury OB switchbox vs. rectifier.

Mercury Rectifier Troubleshooting
The rectifier can remain in place, but all wires will need to be removed from the rectifier.
CAUTION: Make sure the battery is disconnected prior to servicing.
Here are the steps:
Ensure all wires have been removed from rectifier and battery has been disconnected.
Place/set your multimeter to the 1000 ohmmeter reading (RX1K, R X 1000, etc).
Place the RED lead to the ground (G) and place the BLACK lead to A and C alternating. You should show continuity.
Place the BLACK lead to the ground (G) and place the RED lead to A and C alternating. You should NOT show continuity.
Place the BLACK lead to the terminal (B)) and place the RED lead to A and C alternating. You should show continuity.
Place the RED lead to the terminal (B)) and place the BLACK lead to A and C alternating. You should NOT show continuity.
If your results differ, then the rectifier should be replaced.

 

[CharlieB]

Re: 79 Mercury OB switchbox vs. rectifier.

I have a 90 HP L6 Mercury with no spark. I have tested the switchbox and I get no spark from Tue coil wire. Some individuals have eluded to it not being the switchbox but the rectifier, as I consult Dr. Manual Seloc, it doesn't seem like the stand alone 3 post rectifier has anything to do with the ignition system and only has to do with the charging system.
Is that true?
Does the switchbox have a built-in rectifier? It does convert/invert volts somewhere.

If you have a distributor, then the rectifier will not cause a 'No Spark' condition, the problem is either the switchbox or the coil, IF you tested correctly.

 

[Nohfire53]

Re: 79 Mercury OB switchbox vs. rectifier.

Got the new switchbox yesterday, 2986 a8, It's installed and the motor runs great!

Thanks for all you help everyone