84 merc 150 ignition trouble

[dadgummit]

1984 merc 150 has lost fire on #2 cylinder. all other cylinders show strong spark. the rectifier was bad when I got the boat maybe that has stressed some of the other ignition parts. Ive tried a new coil and ive tried switching the stator leads on the switch boxes but the problem stays on that cylinder. Now the parts are getting more expensive and I dont want to waste any more money. Ive checked the stator leads with an ohmeter and it checks out. Any suggestions? Thanks.

 

[Laddies]

Re: 84 merc 150 ignition trouble

The only things that effect 1 cyl on that ign are coil and related wires or a switch box

 

[dadgummit]

Re: 84 merc 150 ignition trouble

The only things that effect 1 cyl on that ign are coil and related wires or a switch box

Thanks Laddies can I switch all the wires from one switchbox to the other and see if the misfire moves? This would confirm a bad switchbox right?

 

[Laddies]

Re: 84 merc 150 ignition trouble

yup, you can switch the 2 boxes around and that tells the story

 

[dadgummit]

Re: 84 merc 150 ignition trouble

well I switched the two boxes and the misfire did move, but it stayed on the same bank.It went from #2 to #6 on the same side. I understood that one switchbox powered one bank, so why didn't the misfire move to the other bank? I actually had spark on all cylinders until the engine got warm and I restarted it then same old story. Does this still sound like a bad switch box? Thanks!

 

[Laddies]

Re: 84 merc 150 ignition trouble

Ck the electric connections and for a shorted wire, also a shorted rectier can act like that disconnect the 2 yellow wires from it and test run

 

[dadgummit]

Re: 84 merc 150 ignition trouble

well I warmed up the ole merc and waited for the spark to die then I pulled the jumper wire between the boxes and the spark came right back. I put the jumper back on and Ive had spark ever since. Replace both boxes or wait and see?

 

[Laddies]

Re: 84 merc 150 ignition trouble

It sounds like a bad bias connection on the boxes and you may have fixed it by cleaning the connections. Its also possible too have an interior bias go bad inside the boxes and thats hard too find without a dva meter. If it was my engine I would run it for a while too see if you have corrected the problem. If the engine has cdi/rapair boxes you may replace one box.

 

[dadgummit]

Re: 84 merc 150 ignition trouble

well I appreciate the advice Laddies if it happens again I'll replace the boxes. have a good one