I more suspect the ballast resistor than the ignition switch. When you start a car or a boat, you apply a full 12 volts to the coil (the ignition switch does this). The starter motor hogs a lot of power, and the coil might not actually see a full 12 volts. Because of this, the coil is actually designed to operate at 6 to 9 volts. Givinig a 9 volt coil 12 volts is sure to give you a good spark. In cold weather, when the battery has less capacity, and the engine requires even more power to get it to turn over, this is especially advantageous. Though the coil might not see a full 12 volts, it is most likely going to see at least 9 volts. Once the engine is running, though, there is no longer a heavy load on the battery (starter motor turned off), and so the battery will supply a full 12 volts (plus what the charging system puts out). You don't want to continuously supply a 9 volt coil with 12-14 volts. You'll burn it and the ignition points (where aplicable) out. That is where the resistor comes in. When the ignition switch is in its normal position, the coil is supplied through a resistor. If the resistor is burned out, the coil won't work in the normal "RUN" position. ...So check your ignition switch and also check that resistor. Resistors are typically about 8 ohms for 12 volt cars and boats, though it varies by coil manufacturer. Higher output coils may require a lower resistance, and lower output coils may require a higher resistance. If you altered any of the wiring of the boat, you may have forgotten the resistor? ...or miswired it? They do burn out from time to time, though.
Thomas
Sep 18, 2007 at 6:47 AM
