How can I test a switchbox?

b.gagnon

Master Chief Petty Officer
Joined
Apr 28, 2001
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835
I have a 1988 or 89 8hp merc that will only fire on one cyl. I swapped the coil, and still no spark from that cyl. Both coils seem to be fine. The motor starts and runs but has no power, seeing it is only running on one cyl. Im thinking switchbox but I have no idea on how to test it. Anyone have any ideas? :confused:
 

Max7

Seaman
Joined
Oct 30, 2002
Messages
72
Re: How can I test a switchbox?

I has the same problem, I coils were good so dind't know if my power parcks were bad so I change my spurk plug and tha was the problem spurk plug was bronken so if if check for spark, doit on the head of the motor not on the spurk plug, if spurk plug are good then is probably your power pack how to test it I don't know tha one,chek your spurk plugs cables conections two. good luck
 

b.gagnon

Master Chief Petty Officer
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Apr 28, 2001
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835
Re: How can I test a switchbox?

The plugs are new, That was the first thing i tried.. Someone told me that the switchbox can cause this, and that it was a problem for this motor. Does anyone know if this is true?
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: How can I test a switchbox?

Yes the switchbox can go down on one cylinder. But as for being a problem with this motor.... I don't think so. This switchbox is the same on merc/mariners from 6hp to 25hp. In 3 years as a boat shop owner I have replaced 1. I'd say that's pretty reliable, wouldn't you....
 

b.gagnon

Master Chief Petty Officer
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835
Re: How can I test a switchbox?

Is there a way to test it with a multimeter?
 

achris

More fish than mountain goat
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May 19, 2004
Messages
27,468
Re: How can I test a switchbox?

Not really.... Do you have a friend with the same engine? You could try swapping it.
 

KCLOST

Commander
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Jun 22, 2002
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2,095
Re: How can I test a switchbox?

Is there a red, blue, red/white and blue/white wire connected to the box at the top?
 

b.gagnon

Master Chief Petty Officer
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Apr 28, 2001
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835
Re: How can I test a switchbox?

The motor is at my brothers house, so i don't know tho colors.....
 

KCLOST

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Jun 22, 2002
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Re: How can I test a switchbox?

IF there is try this... The red, blue, red/white and blue/white wires are the voltage leads from the stator.... <br /><br />They charge the power pack so the trigger leads will release the spark/voltage to the coil at the proper time....<br /><br />Switch the red wire with the red/white..<br />Switch the blue wire with the blue/white...<br /><br />Crank the motor and see if spark moves from one cylinder to another. If there is no change you have a bad switchbox.... If spark moves to the other cylinder the stator is probably to blame...<br /><br />But I'm not sure if you have this type of switchbox or not, so look to see if you have all the wires I mentioned...
 

KCLOST

Commander
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Jun 22, 2002
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2,095
Re: How can I test a switchbox?

Nevermind!!!!! I checked you stator and you only have one set of leads...
 

Max7

Seaman
Joined
Oct 30, 2002
Messages
72
Re: How can I test a switchbox?

just change the switchbox, but before tha change tha swipe the spurk plug from tha one tha you not getting spark if u still doesn't get spark,just change the switchbox.
 

Merc90HPnewbie

Petty Officer 2nd Class
Joined
Jul 27, 2003
Messages
178
Re: How can I test a switchbox?

I have a 90hp inline 6 cyl mercury outboard, after spraying storage seal in the carbs to winterize I pulled the plugs to spray more oil in that side. I noticed one plug was not fouled with burned oil. Turned out that cyl (Cyl #3) was not getting spark. I proceeded like this. To test spark I just pulled the plug out with the wire still connected, and used a car jumper cable to ground the case of the plug to the motor head (because I don't have the stupid $3 spark tester)<br /><br />-swap the plug in cyl3 with another plug. Still no spark<br /><br />-Swap the plug wire between cyl 2 and 3. See if problem follows the wire. Cyl 3 no spark, cyl 2 had spark. Problem is not plug wire.<br /><br />-Replace plug wires, swap coils (move wires from coil of cyl 2 to cyl 3). Cyl 3 no spark, cyl 2 had spark. Problem is not cyl 3 coil.<br /><br />-Replace coil wires, swap channels on the switchbox; move wires from cyl 2 to cyl 3. Now cyl 2 has no spark and cyl 3 does. Problem is in the switchbox or maybe the trigger coil??<br /><br />I replaced the switchbox and now I get spark on all cylinders. Compression test shows approx even compression on all cyls so I guess I got lucky and caught it in time.<br /><br />PS I have the Mercury manual and they say you need a special tester to test the switchbox. The only thing I can think to do is swap the wires for 2 different cylinders and see if the problem moves.
 

b.gagnon

Master Chief Petty Officer
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Apr 28, 2001
Messages
835
Re: How can I test a switchbox?

Just an update....<br /> I changed the switchbox and it is now working!!!!!! next comes the carb rebuild...
 
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