No spark issue on 2,4,6

[Micwlsn91]

Hello all,

New to forum, someone of FB told me this was a good community to get advice so here it goes.


We have a 1985 Mercury 115 Tower of Power Straight 6, engine with No distributor

Maybe someone can assist before the 3 week out Service Appointment.

No Spark on Cylinders 2,4,6

Tried all the obvious, Switched wires out, switched plugs out, cleaned everything.

Changed Switch Box and no change for the better,

(prior to changing switch box I had spark on cylinder 4 but it has since died after switch box Change)

Next step I was going to swap Stator Wires from the switch boxes and see if problem jumps to 1,3,5

After that i was going to test the trigger though the process in the book might as well be in Chinese. Can anyone help me with the process of testing the trigger coils with an ohm meter. Settings and all. I am much better with fuel and air issues.

The other possibility would be the boxes the plug wires come out of. I believe they are called rectifiers. Can anyone tell me the process of testing those as well?

It ran fine when we summarized it but I'm 99% sure the problem started by the negative battery cable on the main battery coming off while smashing through waves. Its tight now, no other blown fuses or problems. Must not have been tight enough but I'm guessing it found a ground to the other battery but not before blowing something we cant pinpoint.

After we couldn't get the engine to stay running when we put in gear we checked out the boat and noticed the battery cable. The other engine ran fine and got us home, so not sure if that was the cause but thought the info might help.

Anyone else have any additional recommendations?

Attached a bad photo just so you have an idea of what I’m working with, I have since replaced some deteriorated wiring though the rest looks fine.

Thanks in advance for any help!!!

 

[jimmbo]

For some odd Quirk, if one Switchbox is defective, you are supposed to replace both. Something about a Bias issue.

 

[Micwlsn91]

Okay! did not think of that. when the sun comes up i will try that. We have 3 other blocks that came with the boat with parts. So we have 6 extra switch boxes. Do you know if there is a way to test them? My luck there is another bad one in the mix, and ill end up using it and moving on.

 

[Faztbullet]

Either stator or switchboxes. The ones you used lay them to the side and use a different pair if stator OK. That wiring is a mess!! Disconnect the idle stabilizer from the switchboxes also

 

[Micwlsn91]

Found another identical motor, on FB. Picked it up and used the switch boxes and wires from it, cleaned up the wiring a bit and it fired right up. Spark confirmed on all 6. Brought it to water to test it in gear and now I'm unable to keep it going in gear, with resistance. Though now that I've confirmed spark, could the issue be with timing? I never removed the flywheel or touched anything that i believe would affect timing. Though i need to rule this out. The boxes from the other engine were a few years older though seem to be the same.

I can get it to idle in gear, with resistance, and making small adjustments allows me to idle up a little, though at some point it will die. Confirmed its getting fuel over and over. If i can rule out it is not a timing issue then i will focus on fuel mixture. Doing another compression test today to make sure that is fine after getting it going. Though we did one not 3 weeks ago and it was fine.

Thank you for your advise so far!