Re: Battery Capacitance Discharge ignition system?
Model number 85393M is a 1973 85hp Evinrude, NOT a Johnson. A Johnson would have a model number of 85ESL73.
The Battery Capacitance Discharge ignition system existed from 1968 to 1972.
The Magneto Capacitance Discharge Ignition system came into being in 1971 on the 50hp model and was widely incorporated on the higher horsepower engines starting in 1973. This exists to this day to my knowledge. This is your ignition system.
You state you have an "intermitent" spark problem, BUT you do not explain exactly what this intermitent problem is..... cranking, starting, break up underway?
This type ignition has a stator under the flywheel that delivers approximately 300 AC volts to the powerpack in order to energize the ignition. The engine must crank over at least 300 rpm in order to provide this voltage. Anything less = weak, erratic, or no spark/ignition.
Closely inspect the stator under the flywheel. There are two large coils that provide the 300 AC volts to the powerpack, one at the very front of the stator and one at the very rear portion of the stator. If there is a sticky looking substance dripping down from the stator upon the timer base and/or powerhead, the stator is failing and cannot provide the needed voltage to the powerpack, in which case, replace the stator.
Spark plugs should be Champion QL77JC4 plugs, gapped at .040 (original recommended gap) or .030 (recommended at some point in the 1990s). Try both settings and compare performance.
Slow cranking engine? With a good known fully charged battery and good known jumper cables, run jumper cables directly from the battery to the electric starter. If you now have a proper cranking engine, you have a voltage drop in the cables/wires somewhere.... remove and clean all cables and wires associated with the starting system, including the battery terminals, solenoid cables and wires, the ground at the powerhead, everything. Also clean the components that the cables/wires attach to.
If there is no change in the cranking rpm when you use the jumper cables directly to the starter, suspect a failing starter.... remove, dismantle, and repair/replace it.
Let us know what you find.
