Ignition System

Tiny
RAIKEN
  • MEMBER
  • CHEVROLET
Ok I am not asking a question that is Car specific. This has to do with the ignition system in a boat, BUT it has a Chevy 350 motor. I am sure this is a very easy question for you guys but I need help. When I crank the motor it fires right up but as soon as I let go of the key the motor dies. If I hold the key on to the start position the motor will continue to run. I put a volt meter on the coil and only have 12v while the motor is cranking, as soon as the key is released I loose the 12v on the coil. I am thinking that I have a bad ignition switch that is only passing 12v in the start position and not in the normal on position, any ideas?
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Monday, June 4th, 2007 AT 8:01 AM

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Tiny
BACKYARDMECHANIC
  • MEMBER
Your probably right to suspect the ignition switch is defective. I wouldn't continue holding the key in the start postion because you are causing the stater to stay engaged and this could cause damage. If you like to make another test you can connect 12 volts to the postive side of the coil and attempt to start the motor without holding the ket in the start postion. I suspect the motor will start and continue to run until the 12 volts is removed from the coil. Good luck and hope this helps :)
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Monday, June 4th, 2007 AT 12:35 PM
Tiny
BIGBADPIRATETOM
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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
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Tuesday, September 18th, 2007 AT 1:47 PM

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