Electrical problems causing stall?

[mooseo]

Can someone explain to me if or how problems with the stator/rectifier cause a motor to stall?<br /><br />I have a 1996 90hp Johnson. It has been having problems that I believe are either the rectifier or stator... the motor will be running ok, then suddenly the tach will go screwy and it will die without warning. <br /><br />This is just ignorance, but I thought that if the battery was connected, even if the charging system failed the battery should keep the motor going.<br /><br />An explaination would be greatly appreciated... I'm scratching my head. <br /><br />thanks,<br />mike

 

[12Footer]

Re: Electrical problems causing stall?

You are looking in the right area,methinks.<br />The rectifier (or intigrated regulator) takes the AC current that the stator generates, and converts it into something your electronics can understand, DC.<br /><br />If there is a poor connection on the rectifier,or it is failing intermittantly, it will (or could) send AC to the tach ,and everything else, causing major screwiness.<br /><br />If you have a digital meter you can clampp-on the output on AC, you might be able to detect it,and confirm your diagnosis.

 

[mooseo]

Re: Electrical problems causing stall?

Hi 12footer,<br /><br />That gets at another of my questions: can the rectifier fail intermittantly? I have tried taking diode readings and things seem OK, but maybe it only fails under load.<br /><br />Could you give me a bit more guidance about what you mean by "clamping-on the output on AC"... do you mean with a induction ampmeter? If so, sigh... I don't have one (yet, I have a feeling I'll have to buy one before this problem is licked). <br /><br />Thanks! <br />mike

 

[mooseo]

Re: Electrical problems causing stall?

Hi 12footer,<br /><br />That gets at another of my questions: can the rectifier fail intermittantly? I have tried taking diode readings and things seem OK, but maybe it only fails under load.<br /><br />Could you give me a bit more guidance about what you mean by "clamping-on the output on AC"... do you mean with a induction ampmeter? If so, sigh... I don't have one (yet, I have a feeling I'll have to buy one before this problem is licked). <br /><br />Thanks! <br />mike

 

[clanton]

Re: Electrical problems causing stall?

Do you have a 60 or 90 degree engine or model number. The ignition system does not need battery voltage to work on 90 degree engine. The stator has 2 sets of windings, the 2 yellow wires are for charging, the brown wires are the charge coils for the ignition system, if engine has Quickstart, it will have a 3rd set of windings for the logic in the power Pack. IF you have a meter, see adapter to read peak voltage at www.esitest.com You need a peak reading meter to check the ignition system.

 

[tesmel]

Re: Electrical problems causing stall?

The most cost effective solution is to replace the bridge rectifier if in doubt. You can get them for far less at an electronics parts store that a clamp on A.C meter. I can buy a 35A bridge for about 10.00cdn.<br />An an electronics technician, I have never come across a bridge rectifier passing A.C current intermittently, I am not saying it can't happen.<br />Hope I have helped.<br />Terry

 

[oldboat1]

Re: Electrical problems causing stall?

I think I would fully disconnect the tach first, in case you have a ground short there. It's possible the motor will run OK when the tach is disconnected (Is the tach an add-on that a prior owner hooked up?)

 

[mooseo]

Re: Electrical problems causing stall?

Thanks for the thoughts... my responses:<br /><br />Clanton, my model number is J90SLEDR. I have to admit that I am a bit confused. I thought that this was a 60-degree loop charged model, but could be totally wrong about that. How do I tell them apart?<br /><br />tesmel, unfortunately, this motor uses a proprietary combined rectifier and regulator that goes for about $200US. That is part of what is making it tough for me because so many of the archived posts recommend swapping out the rectifier when faced with these sort of problems... at your price, I'd do it... at $200, though, I'd like to be sure. Is there any way to check the diodes on a unit like mine?<br /><br />oldboat, I will give that a try... the motor also seems to be having battery charging problems, though. The tach has been on there for about 5 years, and the whole rig was working fine about 2 months ago.<br /><br />tesmel gets at one of my main questions, though... is there any good explaination for why a problem like this would come and go? <br /><br />Thanks for the great thoughts.<br /><br />mike

 

[tesmel]

Re: Electrical problems causing stall?

Mike, if you can start the engine with the Rectifier/Regulator disconnected, then I would do that and see what happens. If you have the same problem, then the rectifier/regulator is good.<br />In my experience I would say that an electronic regulator comprising of semiconductor components can fail intermittently under certain conditions, extreme heat, heavy loads etc.<br />Let me know what happens.<br />Terry

 

[oldboat1]

Re: Electrical problems causing stall?

not to be hard-headed, but I think you need to be careful of running without the regulator/rectifier connected. The stator will continue to produce current -- not a good situation, in my view. And absolutely do not disconnect the battery while running -- will burn out the regulator and/or the rectifier.<br /><br />Electrical shorting can cause sporadic problems --or rather, periodic shorting can cause the on-again, off-again problems. I still think I would lose the tach and see if there is any improvement.

 

[clanton]

Re: Electrical problems causing stall?

The engine is a 60 degree engine. Water cooled regulator with optical ignition. Sounds like you have more then 1 problem. I would start with the engine, then do the charging system.

 

[clanton]

Re: Electrical problems causing stall?

I looked at your old post. The ohm readings you show for the stator test shows the stator is out of specs. I would check OMC manual for specs, different meter and retest, cold engine, the 2 yellow wires must be disconnected. If these test results are within specs, then check output voltage between the 2 yellow wires with a peak reading meter, results should be about 18 volts at idle. Check stator charge coil output brown and brown/white wire, 150 volts with peak reading meter. Check stator power coil output orange and orange/black wire, 50 volts or more with a peak reading meter. The charge coil makes power for the power pack, the power coil makes power for the timer sensor and power pack logic for Quickstart and S.L.O.W. You can also check the plate between the ignition coil and power pack for arcing from coil to plate, each time it arcs and misfires the tach may drop 300 rpms.

 

[mooseo]

Re: Electrical problems causing stall?

Thanks for the suggestions. I am looking through the manual and found the bit about testing the tach circuit from the rectifier. I will go through that tonight.<br /><br />clanton, I think that you are right about multiple problems; I know that I found an air leak into my fuel line that was confounding all this (and fouled my plugs with oil). I have a little improvement after cleaning them. <br /><br />It sounds like the recitifier is bad, but I don't know of a definitive way to test that other than swapping it.

 

[clanton]

Re: Electrical problems causing stall?

On the charging side, you insure the stator is good,if stator is good, then the only thing left is regulator or wires.

 

[mooseo]

Re: Electrical problems causing stall?

I am trying to test that the stator is good, but am having some troubles. According o the Clymers manual, the resistance should be 0.175 but they don't give any units. If I assume that they mean ohms, then that is pretty low... about the same order as my meter leads. Anyway, That is about what I have -- really low resistance in the stator coil and no shorts to ground. <br /><br />Is does this sound like the correct resistance that I am looking for in a stator coil?<br /><br />When a stator fails, does it open circuit or short out? I have continuity on my stator coil, does that sound about right? <br /><br />All the wires hooking up the rectifier look good and seem to have continuity where they should.<br /><br />Does anyone have a suggestion where I can get a rebuilt rectifier/regulator at a lower price that the $200 most shops seem to want to charge me for this?

 

[12Footer]

Re: Electrical problems causing stall?

Sorry for the confusion, I meant to "hook-up" when I said "Clamp-on". I didn't mean to confuse you, and you will need the DVA adaptor from that link Clanton gave you,and a VTVM to hook the adaptor to, in order to test the stator output properly. This is why most guys try the ohms-reading meathod first, and if not to spec, replace the stator.<br />This isn't 100% reliable, which is why the fancy meter adaptor (BTW, thanks, Clanton..I've been looking for one of those that was under 100buks).<br />Schematic was going to send a schematic so I could build my own, but he hasn't been around for a week or so...I hope all is OK at the Shematic-homestead!

 

[clanton]

Re: Electrical problems causing stall?

I think most of the time the OMC stator shorts internaly, because of heat, viberation, and insulation break down. Try these numbers for regulator from Rapair 1-800-851-4296, 1-800-777-0141 in CA.

 

[mooseo]

Re: Electrical problems causing stall?

My meter has a "Max Hold" feature. Is this the same as a peak reading meter? I'm not sure how quickly it responds, however. I'll buy that DVA adapter if what I have isn't sufficient.<br /><br />For testing the stator, is it OK to run the motor with the stator coils disconnected? To get at the brown and orange wires, I need to unplug the bundle from the OIS block, correct? Does it actually need to start, or should I see those voltage spikes as it cranks? <br /><br />If the stator has fried, would that mess up the timing and explain why the motor is running poorly?<br /><br />Thanks for the Rapair distributors; hopefully a rebuilt unit will ease the pain a bit.

 

[clanton]

Re: Electrical problems causing stall?

You need a meter are adapter that will read peak voltage. If you buy a good meter and use it, the meter will pay for itself in money you save on parts that did not be replaced, and you can charge you buddys to check there engine. Three test for each set of windings on the stator, resistance across coil/windings, short to ground, voltage output, cranking rpms only. Check these and post findings.

 

[wilde1j]

Re: Electrical problems causing stall?

I had a similar electrical problem a few years back w/ a Johnson 140 looper. Having a panel voltmeter and ammeter helped diagnose. Symptom was intermittant battery charging. Amps would go to 0 or negative depending on load and voltage went to ~ 12.6 v. Replacing regulator/rectifier was what it took to correct. My recollection is was about $130. I don't think any of the aftermarket mfgrs such as Sierra have OMC rectifiers, although they do have power packs and other electrical/ignition stuff. If you don't already have an installed voltmeter or ammeter, now might be a good time.<br />Jim