Sparks missing, 50hp Merc 1982..

[lede]

Hello!<br /><br />New problem with my 4-cyl. Two lower cylinders are dead. Two upper ones have sparks but the two lower ones have not. Plugs are OK. <br /><br />Is there some common part fot the two lower cylinders that might be broken? Any advise or hint to trace the fault is welcome! Thanks.

 

[ntoracn@yahoo.com]

Re: Sparks missing, 50hp Merc 1982..

I have the same problem on my 20hp. I have spark on one of the two cyls only. Buy a manual and test all of the ignition components. My problem appears to be a $126 switchbox.

 

[lede]

Re: Sparks missing, 50hp Merc 1982..

What is the function of switch box anyway? It seems that the switch box is burnt/broken in my engine too. Tried to switch ignition coils and trigger coils and everything else seem to work.<br /><br />Got one service manual but the wiring diagram didn't help that much. What are the three white wires coming besides the blue and red wires? <br /><br />Is there a danger that the new switch box will burn also or is it just a coinsidence that the old box was broken? I mean, is there something wrong in the engine if the switch box dies. It is pretty expensive box to burn again...!

 

[fishingdan]

Re: Sparks missing, 50hp Merc 1982..

It is not uncommon for switch boxes to fail. I have a 1985 merc 50 and I have had to replace this device once since the engine was new. <br /><br />The switch box is bascially an electronic distributor and points unit. <br /><br />I don't know what would cause it to burn/break. Mine simply stopped working and I was running on 2 cylinders.

 

[ntoracn@yahoo.com]

Re: Sparks missing, 50hp Merc 1982..

I would encourage you to get a manual and test the other ignition components to make sure they are OK and do not cause damage to your new switch box.

 

[lede]

Re: Sparks missing, 50hp Merc 1982..

What is the correct DC resistance of stator between blue - blu/wht and between red - red/wht? It may be the stator that is broken..

 

[lede]

Re: Sparks missing, 50hp Merc 1982..

Has anyone figured out the internal schematic of a 332-5772 (or 114-5772) switch box? Tried to open my old one but the rubber stuff was too much. I´m asking just for the academic interest! It shouldn´t be that complex circuit, the difficult part is the package..

 

[KCLOST]

Re: Sparks missing, 50hp Merc 1982..

Forget about fixing the switchbox....<br /><br />What it does is this....<br /><br />It recieves voltage from the stator. The voltage is "stored" so to speak, until a signal is recieved from the trigger, which at that point the charge is released to the coils/spark plugs to fire the cylinders at the appropriate time.<br /><br />I'm not sure if you can switch the stator leads and retest on that engine or not... But if you can and there is no change the switchbox is at fault if the no spark condition moves to the other two cylinders it means the stator is the problem.

 

[lede]

Re: Sparks missing, 50hp Merc 1982..

No, I'm not trying to fix the broken one. (I bought new switch box and the engine is working fine again). Just interested about the internal structure of the switch box. And maybe some day, if I ever have time enough, I could try to implement similar switch box by myself. It cannot be reliable enough to use it at sea, that's sure. I know what it is like to come home using only paddles if the main engine fails...

 

[johnboywalt]

Re: Sparks missing, 50hp Merc 1982..

I am am just wondering I have no spark on any of 4 cylinders, Merc500 1977, 2stroke. I found a obliterated wire going from what I think is the trigger, I however don't know how to remove it to replace the wire? My manual is on the way