Do I need a new stator or rectifier to get some electricity?

[andy65]

What do you think I should replace to get some current to the battery?
I've done these measurements with a cheap multimeter.
The voltage over the battery is 11.96 V without as well as with the engine running (at idle or higher rpm).
The AC over the stator's yellow and yellow/grey cables is around 6-9 V at idle and 17-20 V at higher rpm, with very fluctuating values.
The DC over the rectifier's red cable and ground is 12.1-12.5 V at both idle and higher rpm, maybe a tenth higher at the higher rpm.
It doesn't seem to be any short circuit between the rectifier's red cable and ground.
I've tested the rectifier and it passes current in one direction to the red, yellow and yellow/grey cables (all in the same direction) but not the other, the resistance is higher in the red cable than the yellow and yellow/grey.
The resistance between the stator's yellow and yellow/grey cable is a little more than 1 ohm.
The resistance between the stator's yellow or yellow/grey cable to ground is less than 1 ohm - is current really supposed to pass from the stator to ground?
So, what do you think, what should I replace to get current to the battery?
Could the low voltage in the battery be causing this, should I run the boat at high speed for half an hour and see if the voltage increases?

 

[tashasdaddy]

Re: Do I need a new stator or rectifier to get some electricity?

what motor? some are only designed to maintain the battery and thats all. and don't charge at low rpms, usually have to be over 2500 for a sustained amount of time.

 

[F_R]

Re: Do I need a new stator or rectifier to get some electricity?

You have to test the rectifier on both yellow wires to red AND both yellow wires to ground. May be two or three yellow wires, depending on what motor. Each test has to be done in both directions. That is, test a yellow to red, then test the same pair with the ohmmeter leads reversed. Should show continuity in one direction, but not when reversed. Repeat for each pair, including yellow to ground.

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

what motor? some are only designed to maintain the battery and thats all. and don't charge at low rpms, usually have to be over 2500 for a sustained amount of time.

It's a Johnson 70 hp VRO from 1986, I think it is supposed to produce 6 A, but I suppose that is at max rpm?

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

You have to test the rectifier on both yellow wires to red AND both yellow wires to ground. May be two or three yellow wires, depending on what motor. Each test has to be done in both directions. That is, test a yellow to red, then test the same pair with the ohmmeter leads reversed. Should show continuity in one direction, but not when reversed. Repeat for each pair, including yellow to ground.

Sorry for being unclear, but I've tested the yellow, yellow/grey and red cable, one at a time, to ground, and then the yellow and yellow/grey, one at a time to the red cable, in both directions, and it passes current in one direction but not the other.

 

[Joe Reeves]

Re: Do I need a new stator or rectifier to get some electricity?

The 1986 70hp Johnson has the small three (3) wire rectifier. Test it as follows, then let us know what you've found. I'm having a problem following your test procedure.

(Small Rectifier Test)
(J. Reeves)

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also). Now, reverse the ohm meter leads and check those same wires again. You should get a reading in one direction, and none at all in the other direction.

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

Note that the reading obtained from the red rectifier wire will be lower then what is obtained from the other wires.

Any deviation from the "Reading", "No Reading" as above indicates a faulty rectifier. Note that a rectifier will not tolerate reverse polarity. Simply touching the battery with the cables in the reverse order or hooking up a battery charger backwards will blow the diodes in the rectifier assy immediately.

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

Remove the rectifier wires from the terminal block. Using a ohm meter, connect the black lead of the ohm meter to the rectifier base (ground), then one by one, connect the red lead of the ohm meter to the yellow, yellow/gray, then the red wire (some rectifiers may also have a fourth yellow/blue wire. If so connect to that also).

Doing this I get a reading from each cable, the resistance in the red seems to be a little higher.

Now, reverse the ohm meter leads and check those same wires again.

And when reversing I don't get any readings at all.

You should get a reading in one direction, and none at all in the other direction.

Do you mean I should get a reading from each cable or from only one cable in one direction (and not in the other direction)?

Now, connect the black lead of the ohm meter to the red wire. One by one, connect the red lead of the ohm meter to the yellow, yellow/gray, and if present, the yellow/blue wire. Then reverse the leads, checking the wires again. Once more, you should get a reading in one direction and none in the other.

I get the same result here, a reading from each cable in one direction only.

 

[Joe Reeves]

Re: Do I need a new stator or rectifier to get some electricity?

The 2nd to last quote.... I mean each cable.

Your results indicates that the rectifier is okay.

With the ohm meter on high ohms, there should be absolutely no reading at all between the stator yellow or yellow/gray cable to ground. If a reading exists, the stator windings are grounded, in which case replace the stator.

Having the ohm meter set to Low Ohms, the reading between the stator yellow and yellow/gray wire should be 1.3 ohms +/- 0.1 ohms.

Let us know what you find.

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

The stator windings are definately grounded, so I'll start with a new stator.

Which leads to the question, how do I make the flywheel come off? http://forums.iboats.com/showthread.php?p=1371839#post1371839

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

Usually I have no trouble finding spare parts on ebay, but I this time I can't seem to find a new stator, which is supposed to have part# 582730, for my Johnson 70 hp VRO from 1986, any suggestions?

 

[Joe Reeves]

Re: Do I need a new stator or rectifier to get some electricity?

You need a flywheel puller that incorporates three holes so that three bolts can go thru those holes to align with the three threaded holes that surround the flywheel nut. Tighten the center spindle of the puller as tight as possible, then hit it hard which should make the flywheel pop loose.

Be absolutely sure to torque the flywheel nut to erxactly 105 foot pounds when reinstalling the flywheel. Any less will result in a sheared flywheel key.

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

The 2nd to last quote.... I mean each cable.

Your results indicates that the rectifier is okay.

With the ohm meter on high ohms, there should be absolutely no reading at all between the stator yellow or yellow/gray cable to ground. If a reading exists, the stator windings are grounded, in which case replace the stator.

Having the ohm meter set to Low Ohms, the reading between the stator yellow and yellow/gray wire should be 1.3 ohms +/- 0.1 ohms.

Let us know what you find.

Now I've changed the stator, but still the engine doesn't seem to generate any current. The voltage over the battery was 12.8 V (charged) at both low and high idle.
Any suggestions?

 

[andy65]

Re: Do I need a new stator or rectifier to get some electricity?

Apparently the rectified is burned now, I guess it wasn't used to the current (the stator has probably been broken for ages).
Can I replace it with whatever rectifier from e.g. a car, could it be a good idea to replace it with a rectifier with regulator included?