murc 115hp 1981 switch box

[captbly]

I need a little help from some one who knows this electrical stuff on these Murcs, got a 1981 115hp inline 6cyl. #4 plug will not fire, checked the coil and it fires. I assume it is the switch box causing the problem. I found a box on ebay, my PN# is 332-7778-A1 the one that is on ebay is PN# 3327778-A12
are they inner changable?

 

[j_martin]

Re: murc 115hp 1981 switch box

They're interchangeable, but if it were mine, I'd be sure both had the same part number. ie both 1's or both 12's. 1,3,5,6,9,or 12 will work. The others probably would also, they are "racing" packs. The hot rodders I know can't see any difference in them at up to 9500 rpm.

hope it helps
John

 

[cannonford57]

Re: murc 115hp 1981 switch box

they are interchangable,..take your # 4 wire and switch it with #5 at the box .its a little trouble but it may save u some money in the long run

 

[captbly]

Re: murc 115hp 1981 switch box

I swapped the #4 to the #5 and the #4 coil did fire. That is what is making me think that it is the switch box, You wouldn't think that it would be the trigger do you? I know that it is one or the other.

 

[trussmonkey]

Re: murc 115hp 1981 switch box

just swap your trigger wires around
each CYL, has it's own trigger wire and coil by playing with the wires it's fairly easy it isolate the problem (trigger, coil or control box)

crank crank your engine (with the carbs empty and ear muffs on, if you crank it without water running to it, you'll be changing the impeller next)

 

[captbly]

Re: murc 115hp 1981 switch box

Thanks I'll try that. Let you know the out come..........

 

[j_martin]

Re: murc 115hp 1981 switch box

A bad trigger will usually take out two cylinders. (because one winding actually drives 2 opposing cylinders.)

A bad stator will usually take out one bank. (because each winding drives one bank)

A bad coil will take out it's cylinder only.

After all that is checked out, the switch box's are a crap shoot, and as I mentioned above they interact with each other through the bias circuit.

Yer on the right trail.

John

 

[captbly]

Re: murc 115hp 1981 switch box

Replaced lower switch box and #4 started firing, then #3 quit firing. Took the top switch box off and replaced it with the old lower on and #3 started firing and #1 quit, do I need to replace upper box also?