metriccrescentwrench
Commander
- Joined
- Oct 22, 2007
- Messages
- 2,598
1981 Johnson 90.
From time to time it was obviously running on just 3 cylinders, but it would always clear up after a little while, making it almost impossible to diagnose. It seemed like it was loosing spark, but it didn't really make sense because the problem usually happened as soon as I put the boat in the water and not after it had been running awhile (which is what I'd have expected if an ignition component were failing).
It happened again while I was pulling my son skiing this week - it was running on 3 cylinders when I "hit it", then after struggling to get on plane for a hundred feet the 4th cylinder started firing again and took off like a rocket (I was impressed, my son managed to hang on through all that).
I checked resistance on all the coils and plug wires again, and this time I actually found a bad plug wire, it showed several mega-ohms. I dissected it to see what was going on and found that the end had been inserted a little off the edge of the wire and was just barely making contact. After enough operation with marginal contact the end started eroding and getting hot, here's what it looked like:
From time to time it was obviously running on just 3 cylinders, but it would always clear up after a little while, making it almost impossible to diagnose. It seemed like it was loosing spark, but it didn't really make sense because the problem usually happened as soon as I put the boat in the water and not after it had been running awhile (which is what I'd have expected if an ignition component were failing).
It happened again while I was pulling my son skiing this week - it was running on 3 cylinders when I "hit it", then after struggling to get on plane for a hundred feet the 4th cylinder started firing again and took off like a rocket (I was impressed, my son managed to hang on through all that).
I checked resistance on all the coils and plug wires again, and this time I actually found a bad plug wire, it showed several mega-ohms. I dissected it to see what was going on and found that the end had been inserted a little off the edge of the wire and was just barely making contact. After enough operation with marginal contact the end started eroding and getting hot, here's what it looked like:
