I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

[NESAR]

Any help would be great;-) When I check for spark its only going on the side shown.Why not the other side? I have 2 pictures here and if you click on them it show the side I have spark on and the side that no spark is on. Please review the pictures in full size.

 

[mmscitrus]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

one of the switch boxes is bad, or both, this is the most likely cause. do you have a Peak reading volt meter? testing is fairly easy if you do, but its a specialized piece of equipment, normal DVI wont cut it.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Can you show me on the motor where the box is located? I think we may have one, but it is to lat to call anyone to find out.

 

[mmscitrus]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

you posted the thread about the mystery wire right? well on that picture the 2 silvery metal boxes on the starbord side of the engine with ALL the wires connected to....those are the switch boxes.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

View attachment 109440
Hope this is a better picture and the correct one it was to small to see if it was the correct side. in the top picture of the motorit shows 1 switch box.
In the lower picture it shows two. I dont see where it is located.

 

[aussieflash]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Yes the top picture on your boat shows both switch boxes.They are sandwiched together.The one you see is the outer.Inside that one is the inner box.

 

[CharlieB]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

It could be caused by a bad Bias circuit on the switchbox that is firing,
OR,
It could be a bad side on the stator.

Two simple tests can help figure it out.

First, disconnect the white Bias wires from both switchboxes, retest for spark. DO NOT START the motor, just test for spark. If you now have spark on all cyls, the original sparking switchbox has a bad Bias and is only good for use on a 3 cyl motor. Original Mer boxes are recommended to be replaced in pairs. If they are CDI boxes it is safe to replace just the one bad box.

Second test, switch the stator leads from one box to the other, if spark switches sides, the stator is bad. This should be verified with a DVA test to PROVE the fault as there is NO RETURN on electrical parts.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Yes the top picture on your boat shows both switch boxes.They are sandwiched together.The one you see is the outer.Inside that one is the inner box.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Yes the top picture on your boat shows both switch boxes.They are sandwiched together.The one you see is the outer.Inside that one is the inner box.

That was nice to no thank you. I was going nuts all night trying to find the 2 of them.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

I will try that today see what it is. but not sure what the DVA test is.

 

[NESAR]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Tried the stator it's not that.

 

[j_martin]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

Tried the stator it's not that.

What's with the sour face? You're the one that decided to just throw money at it instead of getting a DVA, learning how to use it, and doing the diagnostics.

The fastest and least expensive route to a fix is proper diagnostics. There's only about 17,000 viewers on this board that could help you do that. CharlieB is one of them.

 

[aussieflash]

Re: I'm only getting spark in cyl 1,3,5 how come not 2,4,6 merc 1986 175hp

DVA = Direct Voltage Adaptor.You can't just test with volt meter.Get the mercury manual.If yours is a V6 you need the same manual I have.#90-97658-3.