Atlternator help

[psdperformance]

I got a rebuilt alternator after my last one went out. The rebuild shop set it up per my old one ( 2 wire hook up). With the rebuilt alt on the motor i can fire up the boat but i cannot shut the boat off. If i disconnect the alternator and start the boat it shuts off every time???WTF. I do not know much if anything about the wiring for this boat. I put a test light on the positive wire to the alt. and it is hot with the key on or not?? The other wire comes off the alt and goes straight to the Power grid in the back of the boat marked IGN. The wire then splits off to the Ballast resistor. If i connect the ALT. up but disconnect the pirple wire going to the IGN. post i can shut the motor off with the key?
Any help would be greatly appreciated this is getting old quick!!!
Thanks You, Chris

[VAMI]

maybe a bad diode in the alt?I had a car that would feed back but it would shut off then drain the bat as it sat.

[MWJSOne]

Need to put a diode where the current can`t back feed
http://www.alternatorparts.com/7130_7140%20.htm
Its a big problem if you are running a MSD box

[psdperformance]

Where do i install a diode in the system? Is this something internal in the alternator? Sorry for the stupid questions i am still learning about this stuff.:)
Thanks Chris

[inwo]

Where do i install a diode in the system? Is this something internal in the alternator? Sorry for the stupid questions i am still learning about this stuff.:)
Thanks Chris
Connect the diode in series with the purple wire from ign.
Arrow (cathode) pointing to alternator.

[GasGuzzler]

Connect the red wire from the plastic plug to the main alternator terminal. No need to hook the white wire.........done!

[nater1823]

Agreed. GasGuzzler is right, the small wire is supposed to excite the field in your alternator. You have that wire hooked up to the "run" position on your ignition. Am I right so far? When the boat is running, power from the alternator is being fed back to the ignition through that wire. So, when you turn your key off, the field on the alternator isn't dead and your distributor is still seeing power because that too is hooked up to the "run" position, and now your boat won't turn off. I know it sounds strange, but you don't need that wire, :idea: old style GM alternators will be self exciting if you hook the larger red wire up to the charge post on the alternator. Don't be fooled at idle, you may not be charging yet, it's a side effect of hooking it up that way. Most of the time you need to blip the throttle a little to get the field to excite and charge. You should have 14.2 volts. Once the field is going, it won't go dead until you stop the engine. I hope this helps you out a little. :hammer2: