Re: any way to test a switch box???
They need a good 12volt source and can be problematic if cranking volts drop too far.<br /><br /><br />Double check all your grounds.<br /><br />I could suggest you check the wiring around the ignition switch and harness in the motor for fraying, shorts, or opens. Chances are as soon as you start looking over the wiring the insulation can crumble right off. Not much you can do but be careful.<br /><br />I think Mercury made a tester for those that could induce a pulsed source to make it fire off for testing but finding someone with one, or the tester itself for a reasonable price might be tough.<br /><br />I've just been through a couple of those battery/CDI issues and both times "just bit the bullet" and got new CDI boxes.<br /><br />One was on a 20hp that just acted up doing some strange issues with advancing the timing on it's own without reason. Along with hard starting sometimes. That one was like night and day as far as starting with the new box. Now it just fires off so sweet. Manual start too. I think I got that through a dealer for about $250. I think it's available somewhere on line for less.<br /><br />The other was a no spark issue with a 115hp.<br /><br />I checked through some diagnostic procedures I found online at various locations, but every time I tested at the CDI box it was dead. On that one I used the Rapair device with it's own coil for around $200 and that one works real good now too.<br /><br />I do see used CDI switch boxes on ebay from time to time. Sometimes quite cheap. <br /><br />The correct way is to diagnose to find the issue, but that being said....<br /><br />But it's my belief that solid state electronics have come a long way in 30 years and sometimes, a new fresh part might not be a bad choice. Just because of that.
