Pretty common if not using a dropping resistor before the coil.
The coil is oil filled and typical running voltage is more like 4.5 volts with a dropping resistor before the actual coil.
Usually the coil is vacuum packed with oil and allows for expansion when hot. However the coil is sealed and a leak means breakdown of the seals.
Using two ressitances lowers the wattage to each and lowers the heat....you are lucky it ran you home.....
Had it been one of the newer off shore units it would have died ...