Re: How can I test a switchbox?
I have a 90hp inline 6 cyl mercury outboard, after spraying storage seal in the carbs to winterize I pulled the plugs to spray more oil in that side. I noticed one plug was not fouled with burned oil. Turned out that cyl (Cyl #3) was not getting spark. I proceeded like this. To test spark I just pulled the plug out with the wire still connected, and used a car jumper cable to ground the case of the plug to the motor head (because I don't have the stupid $3 spark tester)<br /><br />-swap the plug in cyl3 with another plug. Still no spark<br /><br />-Swap the plug wire between cyl 2 and 3. See if problem follows the wire. Cyl 3 no spark, cyl 2 had spark. Problem is not plug wire.<br /><br />-Replace plug wires, swap coils (move wires from coil of cyl 2 to cyl 3). Cyl 3 no spark, cyl 2 had spark. Problem is not cyl 3 coil.<br /><br />-Replace coil wires, swap channels on the switchbox; move wires from cyl 2 to cyl 3. Now cyl 2 has no spark and cyl 3 does. Problem is in the switchbox or maybe the trigger coil??<br /><br />I replaced the switchbox and now I get spark on all cylinders. Compression test shows approx even compression on all cyls so I guess I got lucky and caught it in time.<br /><br />PS I have the Mercury manual and they say you need a special tester to test the switchbox. The only thing I can think to do is swap the wires for 2 different cylinders and see if the problem moves.
