1995 4.3L Merc. No spark.

[Billy6567]

Any ideas of how to correctly troubleshoot ignition system 1995 4.3L Mercruiser, LX, 4bbl, Thunderbolt IV ignition system. Turns over fine, plenty fuel but no spark. I have replaced the coil, but hoped to not have to replace the Ignition Ctrl Mod. While on the lake it began stalling then running rough and finally quit altogether. It was about 2hrs from 1st signs till it quit working(if that helps at all). I'd like to know how to test the shift interrupter switch. I appreciate any help. Thanks.

 

[dingdongs]

Re: 1995 4.3L Merc. No spark.

do you have a multimeter?you could try disconnecting wire which connects to it.naturally its an open circuit and earths coil out when working under load.remove and test if you can.a manual is a must .
do you have any power at coil and could also disconnect wire that feeds tachometer at the coil as this can earth ignition too.

 

[searay3]

Re: 1995 4.3L Merc. No spark.

There is a flow chart courtesy of Don S for troubleshooting TB4 ignitions. With a meter you will know in 5 minutes what your issue is. Do a search. For some reason I could not find it or I would have given you a link.

 

[John_S]

Re: 1995 4.3L Merc. No spark.

http://www.boatfix.com/merc/Bullet/83/83_24.pdf

http://www.boatfix.com/merc/Bullet/92/92_11.pdf

 

[Billy6567]

Re: 1995 4.3L Merc. No spark.

Got the flow chart. Thanks to all. I'll let you know how it goes.

 

[Bt Doctur]

Re: 1995 4.3L Merc. No spark.

safety lanyard or a bad tach can kill spark too