Re: Spark Plug Wire
Back in the old days, spark plug wire was solid wire core so the 18,000 volts that the coil put out could run rampart, once it jumped the plug gap (less than 100 volts across a fired gap) and the only resistance (impedance) was the secondary of the coil....1800 ohms for a number.
Then came radio's and electronics and it was determined (by whom???) that the current produced by 18,000 volts over 1800 ohms (10 amps thru the plugs) was excessive and the magnetic field produced by that much current got into sensitive electronics.
So some mastermind decided to use a resistive core wire or resistor plug to limit the current which would reduce the radiated field; bonus was that the reduced current prolonged the life of the points.....back when they had points.....and it did.
5,000 ohms (more or less) was a good number for resistance wire (varies with length) or resistor plugs......your answer and worked for years.
Then comes high intensity CD ignition systems with 40,000 volt coils (outboards especially). Accordingly the resistance had to increase to keep the current low to keep interference down.
I would think that a modern outboard has resistance wire because of the electronics that make it run, but I don't know.
But I am willing to go out to my outboard in the shop and pull a plug wire and measure it for you if no one jumps in on this and rescues US.
Mark
