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CDI troubleshooting intermittent spark Need help please 79 Johnson 100hp V4

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kskau36

New member
Hello I am trying to figure out this spark issue with my 79 Johnson 100 v4. First off the boat was given to me by my uncle. He bought it when it was running perfectly 4 years ago (2020) brought it home took it to boat mechanic and had them do a once over just to check compression and overall condition (everything checked out good) so Uncle just parked it after that never used it not once. Fast forward to now 4 years later I inherit the boat and decide to dewinterize and get it fired up. I lubricated the cylinders and did my own compression test and a lot of basics after sitting length of time. Anyhow it fired up fairly easy on the first try (on the muffs). Several days later came back to it and wouldn't start. Had no spark on cyl. #1&3 so I started with all the procedures in the SELOC manual. It is not a key switch kill fault. I put my adjustable gap tester on 7/16 gap watched all 4 cranking it still no spark on 1&3. Cleaned every ground possible every connector. Swapped ignition coils strbd to port side then I get good spark on all 4 so I put back to original location and still have spark on all 4 so I didn't fix anything it just works all of a sudden again. Decided to order power pack and two new coils for stbd side. Installed new power pack and two coils, back to no spark again on stbd side. Then I ohm tested stator and trigger exactly as the manual says and it all within specs. In the meantime I ordered a DVA adapter and while waiting several days I continued on looking for shorts bad wiring etc and retesting ohms short to ground etc. All of a sudden I now get an open reading on stbd side of trigger base. Then I realized I hadn't tested the rectifier well it showed rectifier was toast reading both directions so ordered a new one now it's here just haven't attached the yellow wires yet as I'm afraid I'll burn it out again if there's an issue elsewhere.(Is it possible since the rectifier was bad did it short the windings in the stator? But I'm getting good readings on the tests). DVA shows up so now I can test output voltages disconnected. I'm getting around 2.7v-3v peak value on all 4 on the trigger and 250-300v stator(rectifier disconnected). So I put plugs back in since all of a sudden I have good spark on all 4 again start it up and then it starts running crappy cylinders 2&4 temp at 120 degrees(using laser temp gun) and cyl 1&3 only 90 degrees) so I then assume 1&3 not firing again whem it was just getting spark. Shut it off and put meter on trigger and stator and everything good. Crank it over and now no spark on 1 and 4 weak spark on #2 when it was way good before and weak on #3. Took fly wheel off and can't find anything obvious loose broken wires, no discoloration or melted goo. Put it all back together and cranked it over and watching spark tester you can see all the intermittent no spark then spark. I'll also mention battery is fully charged and good cranking speed as well. I'm really lost and what to pinpoint for sure but I will say one time I did get an open reading on the trigger base. I just need confirmation if I have multiple components failing or should I have reconnected the new rectifier then try again? I don't wanna destroy new components I just put on if something else is causing the others to fail. I need any advice in the order I should be ruling out things please! And thanks in advance!
 
Also meant to ask about the cylinder temp readings in my post earlier, the stbd side was reading 90 degrees while port side was 120. I should just replace the thermostats as it's hard to say how old they are but with the intermittent spark is it possible that's why lower temp due to lack of combustion or thermostats just stuck open?
 
First thing I would do is take starter apart and inspect it.---Post the ohm reading you get from commutator to the shaft.----This test cost no money!
 
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