Pretty much stumped right now

Another long range diagnosis.
2 of the children and their significant others at the trailer right now.
Outboard cutting out very occasionally when idling back to the dock. my son has done some basic troubleshooting and found that there is no spark on any cylinder when it does this. A few hours later it starts right up again with spark as strong as ever. Does not do this when the RPM's are higher and when skiing, tubing etc. Only when idling back to the dock. Power pack has recently been replaced as has the regulator / rectifier and ignition switch. Pretty stumped from where I am sitting at home and needing some ideas and thoughts for when Mrs Ken and I arrive on Friday evening for the weekend hopefully with my Mother in law.
Fuel system has been ruled out by our son and from our phone conversation it is a "no spark" situation. Happened twice in 5 days. All other times they report the boat is running like it always has.
Any advice is much appreciated.
Thanks in advance,
Ken.

Re: Pretty much stumped right now

does it have a kill switch lanyard? Maybe the cap is cracked and getting bumped a bit by an elbow etc when the operator's hand is not on the throttle... That's my WAG... good luck! Hopefully it's something easy, there's not much season left for us northerners...

Re: Pretty much stumped right now

Ken, what are we working on?

Re: Pretty much stumped right now

dis connect the kill wire going to the power pack, and see if it does it again, I would suspect a short in the kill switch or wire..could be a faulty power pack, but it does not sound like it. if you have your DVA adapter and multi meter you can test to see where the power stops once it loses spark.

Re: Pretty much stumped right now

Daviet said:

Ken, what are we working on?

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Sorry, motor in the signature. 1985 Johnson V4 looper.

Lanyard has been by passed for testing purposes and is out of the equation right now.

Re: Pretty much stumped right now

OK... how about check the condition of the wiring en route to the motor. My next WAG is that wires to key switch within whatever sleeve there is covering them on the way to the motor have rubbed together to the point that they can short out. Check close to motor where they'd bend when the motor is trimmed/tilted. Could be that there is larger vibration at idle shaking them around more than at higher rpms. (?) Is the lanyard by-passed at the lanyard end, or at the motor/stator? If the former, it could still be a wiring issue with the kill switch between the lanyard and the motor. Sparkie's test when it has no spark would be definitive (or maybe that's where you disconnected it already?) Also, I'm not sure if the kill wire sparkie refers to grounds the ignition for both the kill lanyard AND the ignition switch, or maybe there is another ignition grounding wire. (?)

Does the control have the plug in type of wiring harness? That looks OK? Has it worked properly since you replaced all the electrical stuff? Maybe you put in a bad ignition switch?

Re: Pretty much stumped right now

Check all electrical connections to make sure they are clean and tight. Also have him disconnect the yellow wires going to the rectifier the next time it stalls out. If she fires right backup there is your culprit.

Re: Pretty much stumped right now

hidef said:

Check all electrical connections to make sure they are clean and tight. Also have him disconnect the yellow wires going to the rectifier the next time it stalls out. If she fires right backup there is your culprit.

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Thanks for the input. rectifier check done and ruled out unfortunately.
Thinking it's somewhere in the 26 year old wiring !!!!
Guess I know what I will be doing on Saturday

Re: Pretty much stumped right now

You could warm up the engine then disconnect the cannon plug and jump the low amp/high amp sides of the starter solenoid and run it without the wiring harness connected. You would have to have a put a wire (with remote starter switch or equivalent) on the black/yellow circuit of CDI to ground out the ignition to turn the engine off. Go and have a run, if the problem goes away, the problem is in the 26 year old wiring harness on the boat side if it stays with you the problem is on the 26 year old engine wiring harness.