Dabbler_E
Petty Officer 1st Class
- Joined
- Apr 20, 2009
- Messages
- 338
My questions is: could a bad connection alone cause sudden, mysterious intermittent spark? Otherwise: stator, timer base, or power pack?
Motor: 1979 Johnson 70 hp
Symptoms:
Saturday -- running nearly WOT, and motor gradually slows, and then stalls once we're off plane. Very difficult to get restarted, only starts with warm up lever up (timing advanced). Dies when I try to get it in gear.
Sunday -- Running very poorly right from the get-go (cold start), stalls unless timing is advanced. Inductive timing light shows one cylinder gets intermittent spark, but the problem moves from cylinder to cylinder.
I take it home and run it on muffs, and get the same intermittent spark problem. Run resistance tests on stator (550 ohm) and sensor coils (18-20 ohm) -- both right in specs according to factory service manual. During this procedure I disconnected all the wiring harnesses going to and from the power pack.
Reconnect harnesses and start it up again -- now running fine. All cylinders getting decent spark.
Today: running fine. All cylinders getting good spark. All snap blue spark at 7/16" gap.
Borrowed an oscilloscope and the 3 sensor coils are all throwing 3v.
Now I'm in a quandry. I'm getting the sneaking suspicion that the original problem was gunk/corrosion in one of the wiring harnesses causing a gradual voltage drop that finally dropped below a threshold where the motor could function correctly. If so, I don't care to spend $80-$180 for a power pack or timer base if I don't need to, but I also don't care to get stranded again.
Have any of you outboard service pros had a similar problem caused by just bad connections?
Motor: 1979 Johnson 70 hp
Symptoms:
Saturday -- running nearly WOT, and motor gradually slows, and then stalls once we're off plane. Very difficult to get restarted, only starts with warm up lever up (timing advanced). Dies when I try to get it in gear.
Sunday -- Running very poorly right from the get-go (cold start), stalls unless timing is advanced. Inductive timing light shows one cylinder gets intermittent spark, but the problem moves from cylinder to cylinder.
I take it home and run it on muffs, and get the same intermittent spark problem. Run resistance tests on stator (550 ohm) and sensor coils (18-20 ohm) -- both right in specs according to factory service manual. During this procedure I disconnected all the wiring harnesses going to and from the power pack.
Reconnect harnesses and start it up again -- now running fine. All cylinders getting decent spark.
Today: running fine. All cylinders getting good spark. All snap blue spark at 7/16" gap.
Borrowed an oscilloscope and the 3 sensor coils are all throwing 3v.
Now I'm in a quandry. I'm getting the sneaking suspicion that the original problem was gunk/corrosion in one of the wiring harnesses causing a gradual voltage drop that finally dropped below a threshold where the motor could function correctly. If so, I don't care to spend $80-$180 for a power pack or timer base if I don't need to, but I also don't care to get stranded again.
Have any of you outboard service pros had a similar problem caused by just bad connections?
