Stator problem

I have a 1997 90hp Johnson TSLEAU. last time out battery went dead out on the water. i've had some concerns on wether or not my battery was charging from the sator because the volt meter never reads above 11 volts
this saw also comfirmed by the volt meter on my fishing graph. I have a 6amp unregulated charging system on my motor. Also the other thing I noticed was my tach would drop to 0 rpms and than back to normal rpms. This is a new tach alos the old tach did the same thing. I've did ohm test on the staor and it doesn;t check according to the service manuals I have. Any thoughts would be appreciated.

THANK, kEVIN

Re: Stator problem

Two things to check. Firstly the stator coil for continuity. You've done that! If the resistance is close to that given in the manual then it is possibly OK but you cannot test for shorted turns with a multimeter. If the resistance is high (infinity) then the coil is open circuited.

The second thing to check is the rectifier. You say it is the (round) unregulated type. That can be checked by following Joe Reeves' directions on the "Engine Frequently Asked Questions " board.
BUT if you use a digital meter use the "diode test" range as they do not always work for diode testing on the Ohms ranges.

You can also check the output from the stator coil using an AC voltmeter.

If you have let you battery fall to 11 volts regularly or have not charged it promptly after even partly discharging it then it has probably had it!

Do not discharge a battery, other than a deep discharge one, below 50% of its capacity on a regular basis and do not leave an even partly discharged battery for longer than absolutely necessary before recharging it.

As rough guide the volts of a battery that has not be used or charged for 12 hours should be at least 12.7 if fully charged, will be about 11.7 if effectively discharged and about 12.2 if half charged.

Re: Stator problem

If you megger the coil you can determine if there is a short. the megger test should read 10,000 ohms to infinity. anything under will indicate a shorted winding. the lower the reading the fewer windings are actaully being used.

Most electricians will have a portable megger, or anyone that tests motors.

Re: Stator problem

If you megger the coil you can determine if there is a short. the megger test should read 10,000 ohms to infinity. anything under will indicate a shorted winding. the lower the reading the fewer windings are actaully being used.

Click to expand...

pardon?

The coil itself should have quite a low resistance .. a few ohms only.

There should be a very high resistance between the coil and ground .

The ohms ranges on a multimeter will be adequate

Re: Stator problem

when you megger you are measuring the leakage from the coil. the more resistance the better the coil. its the same when you megger generators.

Re: Stator problem

when you megger you are measuring the leakage from the coil. the more resistance the better the coil. its the same when you megger generators.

Click to expand...

You are talking about the resistance between coil and ground then and
your reference to shorted turns is a short to ground.

Not irrelevant but the OP should be measuring the actual resistance of the coil to check that it is not open circuited.

Re: Stator problem

Thanks for your quick replies..........Also rechecked the ohms check on the stator and it checked out at 1.3 ohms which is correct in the manual specs.

I never knew that the unregulated system required so much keeping an eye
on. I never thought to recharge my battery between trips as this was just the starting battery although I do have both graphs hooked up to the starting battery. I did have the starting battery checked out and the parts store did it still was in good shape. I always recharge my trolling motor batteries immediatley after returning home. But will keep and eye on the starting battery.
I wonder if putting on a voltage regulator would be a better upgrade?
I believe that all I would need is the regulater/rectifier. The stator is the same for both models if the web sites I looked are correct.

I could get access to a meggar. Would I use the yellow and yellow with tracer to make the test.
And what about the ac voltage measurement. What would it be and at what rpms?

Thanks again Kevin

Re: Stator problem

You have done the resistance test between the two yellows. That's come out correct. That's good but it does not eliminate the possibility of shorts between turns.

If you can get old of a Megger test between either of the yellows and ground. That will test the insulation and the resistance should be v.high.

You should get an AC volts reading between the yellows rising through 12 to 14 and up to 18 or 20 maybe as you increase the revs.

The fact that you have an unregulated rectifier should not be of any concern. It is only the higher output stators that require a regulator to prevent them over charging the battery. That does not seem to be your problem... rather the opposite.

Having checked the stator now test the rectifier. Use the diode test range of your multimeter.
Test between the red wire and each of the yellows and between the case (ground) and each of the yellows. Each time do a measurement then reverse the meter leads and do another measurement. You should get a low reading one way and a high ( infinite) reading the other way.

If you also test between the case and red you should get a high (infinite) reading one way and a low reading the other. If you test between the two yellows you should get a high (infinite) reading both ways.

I'd bet that you'll find that the rectifier is blown!

If at any time you have connected the battery with the polarity reversed you will have blown the rectifier. Something you must be very careful about!

Re: Stator problem

Is 7500 ohms to high/low on the low side? I get infinite on the high side.

Thanks,
Kevin

Re: Stator problem

the diode test range actually measures forward volts drop in mV , not resistance in ohms

If you you have not misread it 7500 is too high. I'd expect something between 600 and 700. 750 might be Ok but not 7500.

Re: Stator problem

Aha!
I believe I've solved the problem. You are correct sir about it being around 750 ohms. I had a friend of mine double check my testing of the diode. And he got a bad reading on the yellow tracer leg. It really perplexed me that he got a bad reading and I didn't. So I tried testing it again by myself and it showed alright. After the third time I finally got a bad reading and much to my surpise when I had the wire in a strectched position it read bad. You could see the needle jump up and down the scale. Evidently that is why the battery was running down and probably why my tach was going dead and than working. I hope I didn't burn the stator up.

Just when think you've seen it all,
Thanks again for your advice,
Kevin