'76 Merc 85hp 850 Thunderbolt: Faulty Ignition Switch frying switch box?

[Dentcrew]

OK, here's what I have: No Spark, narrowed down to Switch Box: Trigger and Stator Tests within range both Ohms and DVA. Nothing coming out to Green Wires ( to the Coil Packs ) from the switch box (Power-In no Power-Out). However, when the "Kill Switch" Wires are connected to a DCV to via Back/Yellow to Ground on a Multi meter, with the "Orange wire disconnected from the Switch Box ), as I have a newer Control Box and newer Harness to engine (Per CDIElectronics Diagnostics), I get a reading (Not much but some @ the 500v DC Setting) every time the key switch (ignition switch) is turned on/off/on/off/on, I get a reading (fluctuation). Which would indicate a Faulty "Ignition Switch" which is "Most Likely" frying the API Switch box? So,if I change the Switch Box out, it should just "Fry" again at $200+correct? So, change the Key Switch (Ignition Switch) AND Switch Box to resolve?

 

[Chris1956]

Hard to follow your post...You will not normally have power to the coils, with the ign on. The coils are pulsed by the switchbox, when it is time to fire the spark plugs. A normal multimeter will likely not be able to read the pulse, however, you should be able to see the spark on the spark plug, if (obviously) coil, switchbox, wiring and trigger are all good


I am not sure if the voltage you see on the ign killer wire is enough to fry the switchbox. Does CDI electronics have a test for your switchbox? If so, you could run it. I would D/C ign killer wire for duration of testing. Ign switches are cheap. If in doubt, replace it.

 

[Dentcrew]

New Switch Box Arrived and Installed. Runs great, however, will not run with the Kill Wires attached to the Switch Box, and the bad part, without them attached, it will run, but won't turn off with the key. Have to pull the choke to flood it to die. Bad key switch I suspect? If so, any idea how I would find that part number, as I have a newer model control box for that engine?