I have a 1994 mercury 125 outboard that just quit running while on the water one day. I quickly found out I wasn't getting a spark on any of the 4 cylinders. Using the shop manual from mercury I have performed various measurements. I disconnected the kill circuit and still no spark. I disconnected the yellow wires between the stator and rectifier and still no spark. I then disconnected all stator wires and I measured the impedance of the stator and it seems to be outside the acceptable range as specified in the manual. Then with all the wires still disconnected I measured the AC voltage accross the red - red/wht and blue - blue/wht wires and they both read low (125VAC, and 12VAC) from what the manual indicated, although I wasn't using a DVA (just a regular digital voltage meter set to measure volts AC. I then disconnected all wires from the trigger and measured the impedance on them as specified in the manual and all seemed well. I did a visual check on the voltage regulator and found burn marks on it near where the wires come into it. I also performed the diagnostic measurements specified in the manual and it appears that the voltage regulator needs replacement as well. The manual didn't mention how to test the switch box but I am wondering if it is bad as well. How do I test the switchbox on my motor? I am also wondering what caused the voltage regulator to blow out? Is this likely to happen again?<br /><br />Any suggestions would be appreciated on how to proceed.<br /><br />Thanks.
<br /><br />Loose, corroded, or crossed battery connections damage the voltage regulator 90% of the time.<br /><br />The switchbox is tested with a DVA adapter. Basically you test what's going in and what's going out with it. If you have resistance between the stator wire pairs, it's probably OK. Also check for shorts to ground. There should be no continuity between any of those leads and ground. There should also be no continuity between pairs (ie. no continuity from red to blue to yellow, just between reds, blues, and yellows).<br /><br />Switchboxes fail about as often as stators. My guess is that your switchbox failed. But I wouldn't take that to the bank without testing it first. It's an expensive gamble.