Mercury 150 Spark on Only 2 Cylinders

snowbrd84

snowbrd84

Petty Officer 1st Class
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Sep 23, 2012
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I have a Mercury 150 XR2 (1986) I just picked up and put on my boat, tried starting it and realized it was only getting spark on cylinders 4 and 6. I tested all coils, all are perfectly within the Ohm range in the manual. Trigger test came out perfect per the manual. I disconnected the yellow/black kill wires, no change. disconnected the rectifier, no change. The Ohm reading on two of the Stator wires were a little high. Also, some of the stator wires are very corroded. Could the stator cause this issue? I tried swapping the number 5 and 6 coils, the coil i moved from 6 (was firing) to 5 no longer fired, and the coil i moved from 5 (wasnt firing) to 6 now worked. So it is not the coils.
 
C

Chris1956

Supreme Mariner
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Mar 25, 2004
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27,142
Re: Mercury 150 Spark on Only 2 Cylinders

Why not run the troubleshooting test on the CDIElectronics web site? In general triggers are shared between 2 cylinders and switchboxes between 3 cylinders.
 
snowbrd84

snowbrd84

Petty Officer 1st Class
Joined
Sep 23, 2012
Messages
215
Re: Mercury 150 Spark on Only 2 Cylinders

I already pulled the stator, i was just wondering if this sounds like a stator problem. What about the trigger? What exactly does the trigger do?
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,142
Re: Mercury 150 Spark on Only 2 Cylinders

The trigger tells the switchbox when to fire into the coil. There are three triggers.
 
snowbrd84

snowbrd84

Petty Officer 1st Class
Joined
Sep 23, 2012
Messages
215
Re: Mercury 150 Spark on Only 2 Cylinders

Got the new stator, installed it, same exact problem, no change. Decided to try swapping wires on the switch boxes. After swapping the front box to the back, back to the front, now have spark on 1,3, and 5. So turns out it was the switch box, not the stator. And i think the #2 coil might be bad, which is what threw me off. If i had spark on 2,4, and 6, switch box would have been obvious. Its odd though, i tested each coil with my ohm meter and they were all perfect. Can the coils test ok with the ohm test but still be no good? Im really hoping a new switch box and coil and this thing will fire up...
 
7

79Glastron

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Jul 18, 2007
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Re: Mercury 150 Spark on Only 2 Cylinders

Mercury recommends replacing switch boxes in pairs.
 
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