No Spark resulting in Tow of Shame 7.4L Thunderbolt 5 ignition

[OldNBold51]

While going down the lake after 10 minutes run time, the old girl just quit, almost like I'd turned off the key. Gas showed 1/2 tank and visually saw AP squirting in carb. A spark check showed nothing. nothing at the plug when grounding at engine, nothing at the coil wire to distributor cap.

The above was my early diagnosis on the water with basic tools in the boat. Once back at the dock, all I had was a multimeter. The manual was at home in the computer. My only check with the meter was battery showed 12.65 volt and the bullet connectors wires leading to the distributor showed 7.5 volts. At that point i pulled the distributor and brought it home
thinking that's a low reading and a good place to start looking. upon reading the manual, all it says in the troubleshooting was "0 volts, replace ignition module".

So all you experts, help me out here. Where do I start/continue?

serial # OF437981 95 wellcraft232 190 hrs on rebuilt engine

 

[Don S]

Re: No Spark resulting in Tow of Shame 7.4L Thunderbolt 5 ignition

Here is the diagnostic chart. Should help you find where the problem is.

 

[OldNBold51]

Re: No Spark resulting in Tow of Shame 7.4L Thunderbolt 5 ignition

Thanks Don.

I checked #4 and the white/red only showed 7.5 volts. What I didn't do, was check #3, as I didn't have the manual with me.

If the white/red leads only show 7.5 volts, how will that affect fire?

 

[Don S]

Re: No Spark resulting in Tow of Shame 7.4L Thunderbolt 5 ignition

Print out the chart, and do the tests in order. A single voltage out of a single test in the middle of the troubleshooting chart means little.

 

[OldNBold51]

Re: No Spark resulting in Tow of Shame 7.4L Thunderbolt 5 ignition

Update: got her running, It was the coil that went bad. however: during the testing, specifically when you do the rapid grounding of the white/green wire, I never got a spark even after I had installed a new coil (I bought coil and a ignition trigger, planning on bringing 1 or the other back to refund). Can someone answer me this: during my testing, my coil wire looked a bit suspect so i checked continuity with a multimeter. I showed no continuity. Hoping that surely my problem can't be this easy to fix, I was going to substitute a plug wire for the coil wire. I checked continuity on it and got no reading. Is there a reason that the same coil wire and the plug wire, which I used to get the boat running, don't show continuity using a multimeter?

Even though i showed nothing during the checklist, I had an inline spark tester so I gave the starter a few turns and instantly showed spark. A little gas and she fired up! Wish i knew why my test procedure never showed any spark, even with a new coil installed.