1984 mercury 90 missing on 246 kinda

[superman111]

I lost spark on 246 at the lake got home and didnt have any on any cylinder. I seen my stator had a whole burned in it, i replaced it today and got spark back on 135 really hot, now i have a fading spark on 246, so I swapped stator leads and same thing, so i assume that there is a problem with the switch box or the wiring to it, does this sound right? or is there another likely possible fault that i havent considered? Thanks

 

[daveswaves]

Re: 1984 mercury 90 missing on 246 kinda

Likely switchbox, both would be wise.

 

[superman111]

Re: 1984 mercury 90 missing on 246 kinda

one of the switchboxxes has allreaddy been replaced,the one that wasnt replaced is the one at fault, but why does it have spark like on the first revolution then no more, could there be a bad ground that would cause this. and is there any chance that the trigger could be bad, i really wanna narrow it down so i dont end up buying something i dont need?and would it be likely that the stator and a switchbox would go out at the same time?

 

[daveswaves]

Re: 1984 mercury 90 missing on 246 kinda

There is a bias circuit in the switch boxes that is common to both, it is connected by a white wire running between them. Unfortunately, sometimes when a switch box or stator goes it takes out the other switch box as well.

 

[superman111]

Re: 1984 mercury 90 missing on 246 kinda

so in other words when the stator went it took out one of the switch boxes with it? still waundering if there is a possiblity with the trigger being bad, I wouldnt think so bc the triger isnt divided into 246 and 135 is it? Now that i do have a hot spark on 135 there isnt any way it could be bad right, that only means it could be the one that runs 246? So then it is not a coincodence that the stator and one switch box went out at the same time?and one other question if i had a dead battery that wouldnt take a charge is that likely what burned out my stator in the first place or do they just burn up over time?

 

[daveswaves]

Re: 1984 mercury 90 missing on 246 kinda

The defective battery likely led to your stator burn out. The trigger will be fine. Your switchbox that runs 246 is defective.

 

[CharlieB]

Re: 1984 mercury 90 missing on 246 kinda

Disconnect the White Bias wire connecting the two boxes together and retest for spark.

If you now have good spark then you have a bad Bias one the 135 box, the defective odd box is blocking the even box from firing.

OEM boxes are recommended to be replaced in pairs, you said one box has already been replaced, if the good box is a CDI Electronics then it is safe to replace only the defective box.

Note; A box with a bad Bias will work perfectly fine on a 3 cyl motor. Mark it 'Bad Bias' with a paint pen and pass it on, another user may still benefit from it.

 

[daveswaves]

Re: 1984 mercury 90 missing on 246 kinda

Disconnect the White Bias wire connecting the two boxes together and retest for spark.

If you now have good spark then you have a bad Bias one the 135 box, the defective odd box is blocking the even box from firing.

OEM boxes are recommended to be replaced in pairs, you said one box has already been replaced, if the good box is a CDI Electronics then it is safe to replace only the defective box.

Note; A box with a bad Bias will work perfectly fine on a 3 cyl motor. Mark it 'Bad Bias' with a paint pen and pass it on, another user may still benefit from it.

I agree Charlie, however he changed the 135 box with a new one so I suspect the bias circuit in 246 is bad, which will also prevent it from firing correctly. One way or the other he should be able to eliminate the problem box by swapping and see where the problem goes. Removing the white wire is a good troubleshooting trick, thanks for reminding me.

 

[superman111]

Re: 1984 mercury 90 missing on 246 kinda

Alright thanks for the tip, I am going to go try that right now. And yes the 135 box was replace with a cdi box, so if by removing the white wire i get spark then do i need to replace that box or what? Again thanks.

 

[daveswaves]

Re: 1984 mercury 90 missing on 246 kinda

Alright thanks for the tip, I am going to go try that right now. And yes the 135 box was replace with a cdi box, so if by removing the white wire i get spark then do i need to replace that box or what? Again thanks.

If you remove the wire and 246 works then your new CDI box is bad, which is unlikely. If you remove the wire and 246 does not change (ie still flaky spark) then 246 box is bad. If you want to confirm that you have the correct box, swap them, the problem should move to the other cyl (135).