Hello everyone.
I have an old mercury 500 model which appears to be from 1976. One of the problems I am having is that spark is present only on cylinders 3 and 4. Having no repair manual nor prior knowledge of outboard engines I started poking around and this is what I have discovered so far.
Stator has two windings which connect to the switchbox (blue + blue white and red + red white)
My thinking was that one coil powered ingnitors 3 and 4 and one coil powered ingnitors 1 and 2. I noticed that switching the red + red/white wires for the blue + blue/white wires now resulted in spark in cylinder 1 and 2 and no spark in 3 and 4. So I figured that the red winding must have a fault in it (I determined it was the red one by disconnecting one winding at a time to see when the sparking went away) . I then decided to jumper the blue/white wire to both the red/white and blue/white terminals on the SB and the blue wire to both the red and blue terminals. Sure enough, there is now spark on all 4 cylinders. Great, problem solved, there is clearly a problem with the red winding.
Now, here is where I run into my current state of confusion. I then do some more research and find out that the two windings in the stator are not meant to be identical. One is not dedicated to cylinder 1 and 2 and the other to 3 and 4. Apparently one is a high speed winding meant to generate adequate voltage at high rpm and the other is for lower rpm. Which explains the coil resistance differential. Ok... then why did swapping the coils result in the sparking set of cylinders to also swap?!
I hope my explanation is clear. Does the observed behavior make sense to anyone? What is going on?
Thanks,
Alex
I have an old mercury 500 model which appears to be from 1976. One of the problems I am having is that spark is present only on cylinders 3 and 4. Having no repair manual nor prior knowledge of outboard engines I started poking around and this is what I have discovered so far.
Stator has two windings which connect to the switchbox (blue + blue white and red + red white)
My thinking was that one coil powered ingnitors 3 and 4 and one coil powered ingnitors 1 and 2. I noticed that switching the red + red/white wires for the blue + blue/white wires now resulted in spark in cylinder 1 and 2 and no spark in 3 and 4. So I figured that the red winding must have a fault in it (I determined it was the red one by disconnecting one winding at a time to see when the sparking went away) . I then decided to jumper the blue/white wire to both the red/white and blue/white terminals on the SB and the blue wire to both the red and blue terminals. Sure enough, there is now spark on all 4 cylinders. Great, problem solved, there is clearly a problem with the red winding.
Now, here is where I run into my current state of confusion. I then do some more research and find out that the two windings in the stator are not meant to be identical. One is not dedicated to cylinder 1 and 2 and the other to 3 and 4. Apparently one is a high speed winding meant to generate adequate voltage at high rpm and the other is for lower rpm. Which explains the coil resistance differential. Ok... then why did swapping the coils result in the sparking set of cylinders to also swap?!
I hope my explanation is clear. Does the observed behavior make sense to anyone? What is going on?
Thanks,
Alex