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what is a stator

Old 05-09-2003, 04:55 PM
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Default what is a stator

kind of in the dark about engine repair. i know the basics and how the engine works but i need somebody to explain what a stator is and what it does. how many in an outboard (1?), etc.
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Old 05-09-2003, 05:16 PM
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Default what is a stator

The stator is the "stationary" part, with windings, that lies under the rotor, or the "rotationary" part that revolves as the flywheel spins. The rotor/flywheel has the magnets around its ID perimeter and the result of the magnets spinning around the windings produces AC current.

Your rectifier converts the AC current into useable DC voltage that is controlled or "regulated" by the OB's voltage regulator.

Hope this helps ...

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Old 05-09-2003, 05:26 PM
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Default what is a stator

in plain english.......kinda like an alternator on outboards (and some I/Os)
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Old 05-09-2003, 05:58 PM
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Default what is a stator

The part of an electric motor that don't go round and round.
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Old 05-09-2003, 07:32 PM
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Default what is a stator

What Reel said,
The flywheel has magnets on it’s underside. The stator is a donut shaped bundle of wires that’s under the flywheel. As the flywheel turns the magnets induce an electrical current in the stator. Nowadays, the rectifier and regulator are combined in a single unit. The stator may have several windings in it- one for the spark, one for the 12 volts D.C to charge the batteries and run the electronics, and one for a timing signal to let the power pack know where the flywheel is, but there’s only one stator on an outboard.
About the only way to hurt one is to mess up the regulator first. If the regulator tries to draw too much current, the windings in the stator overheat, the insulation melts, then the windings short out and don’t provide enough current. So if you have a problem with your batteries, those windings can short out your spark windings, and the motor will die from weak spark.
Stators don’t often go bad, and when they do, it’s probably because the regulator is bad (at least in johnyrudes). To test them, you can measure the resistance of the coils using the factory manual. When a johnyrude stator shorts, the insulation (“ potting compound”) melts, and you can see a thick black tar-like substance dripping if you look under the flywheel with a flashlight.
New engine flywheels and stators are keyed, so you can’t put ‘em on wrong, but the older models have to be timed if you remove them.
I replaced several on my ’90 model 70hp johnsons before I replaced the regulator. After that, it was smooth sailing. I think I killed the regulator by jump-starting the engines after a battery died. Damn expensive education.
May all your electrons flow smoothly. chip.
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Old 05-09-2003, 08:15 PM
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Default what is a stator

Uh oh. I've jumped my motor a few times when the battery was dead. Always lit right up without a problem. What is wrong with jump starting an outboard? I always followed the same procedure as when jumping another car.
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Old 05-10-2003, 05:54 AM
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Default what is a stator

Alex T,
First let me say I'm not sure that's what killed mine, so you may be fine. Second, my motors were '90 johnsons, other manufacturers may not have that problem.
But here's what I think happens: The output device on the regulator is a zener diode. Zeners are suseptible to blowing if they are forward biased. So, when you jump start the motor, if the motor being jumped produces less current than the motor jumping it, current will flow the wrong way in the regulator, the zener dies, the regulator sucks too much current from the stator, and the stator windings melt.
After I jump started them, I ran the motors 10 to 20 hours before one of the stators finally croaked. It's a gradual thing.
If your stator is being damaged you can see signs of it by looking up under the flywheel. You should be able to see the bottom of the stator. It should appear black and smooth. When they overheat you can see the potting compound dripping- it looks like black candle wax. Also, before the motor dies, the resistance of the stator winding is lower than the specs.
I don't know how to test the regulator after the motor has been jump started. I think it still works- that is it still puts out 12 volts- but I think there is too much AC ripple riding on the 12 volts, but I'm not sure.
I hope your stator and regulator are OK. Good luck. chip.
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