Somebody probably had a wore go bad and had an old automotive one laying around. The 10.000 Ohms is likely 10,000 Ohms per foot. Sounds like a lot, but compared to the impedance of the spark gap, it is insignificant for car engines. For some reason, it seems to be more significant for outboards. Back in the day, it was not uncommon for all spark plug wires on a car to be made from this stuff, not just the coil wire.