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Testing Stator and Trigger on 1986 Mercury 35hp

P

Phillips_211

Member
OK I have done the tests on my stator and trigger.
35
1984-1989
6445653-OB393190
332-7452
3200-3800
225-300
180V+
20V+
Blk/Yel (LS) Blk/Wht(HS) to Eng Gnd
750-1400
0.5V+
Brown/Yellow to Brown/White
0.2-1.0
800-1100

For my stator I am getting 1500ohms on LS and 149ohm on HS Unlike the 3200LS and 225HS. Im thinking this is the problem
For the Trigger Im getting 800 ohms which should be good.
But one question For the stator wires that go into the CDI and come out I don't get any ohm reading at all on them? Is this a problem or does the CDI have to have power running to it to get a ohm reading?
 
I would be worried if your stator ohm reading were higher indicating some loss of continuity with the windings - I wouldn't sweat these numbers at this point.

You will not get continuity from the switch box it's a multi-circuit piece of gear.

Power from the stator goes to the CDI and is rectified (converted from AC to DC) and then stored in a capacitor (normally one per cylinder) after passing through a "blocking diode" that prevents the power from "backing up" back into the stator.

The release from the capacitor is controlled by a SCR switch (silicon controlled relay). The SCR lets the capacitor discharge to the appropriate sparkplug when it gets an AC pulse (short burst of energy) from the Trigger. The trigger produces a "positive AC" pulse the first time the magnet passes it (which "triggers" the cylinder one capacitor) and then on the second pass of the magnet a "negative AC" pulse signals the SCR to "switch" and release the power from capacitor "2", for the second cylinder (this is how Merc 2 cylinder triggers work - with more than two cylinders it's a little different but the effect is the same).

So.... There is no way to check continuity from the swithbox (CDI, Powerpack - pick your name). Generally, you prove everything else is working and replace the box as the final option...
 
galamb said:
I would be worried if your stator ohm reading were higher indicating some loss of continuity with the windings - I wouldn't sweat these numbers at this point.

You will not get continuity from the switch box it's a multi-circuit piece of gear.

Power from the stator goes to the CDI and is rectified (converted from AC to DC) and then stored in a capacitor (normally one per cylinder) after passing through a "blocking diode" that prevents the power from "backing up" back into the stator.

The release from the capacitor is controlled by a SCR switch (silicon controlled relay). The SCR lets the capacitor discharge to the appropriate sparkplug when it gets an AC pulse (short burst of energy) from the Trigger. The trigger produces a "positive AC" pulse the first time the magnet passes it (which "triggers" the cylinder one capacitor) and then on the second pass of the magnet a "negative AC" pulse signals the SCR to "switch" and release the power from capacitor "2", for the second cylinder (this is how Merc 2 cylinder triggers work - with more than two cylinders it's a little different but the effect is the same).

So.... There is no way to check continuity from the swithbox (CDI, Powerpack - pick your name). Generally, you prove everything else is working and replace the box as the final option...
Click to expand...

OK, But do the readings I have mean that the stator is most likely bad?
 
Nope - if there is excess resistance (loss of continuity) then the stator may not be producing enough power.

If there is NO continuity then one of the bobbins is probably broken = no power.

With "less" resistance that indicates the windings are fine and are not grounding out. You could have the stator tested with a DVA equipped meter to see exactly what voltage it's putting out, but with those readings I would NOT suspect an issue with the stator...
 
OK, is there any way to test voltage with a regular multi-meter? I have one that measures AC and DC volts. Also I just found out this motor has a mercury switch that prevents the motor cranking when it is in the up position. If this part was faulty could it be the reason for no fire?
 
You can use a regular multi-meter but it requires a DVA adaptor between the meter and the stator.

The DVA acts like a rectifier to convert the AC (which if you measure the AC from the stator gives you a "meaningless" value) to "persistant" DC which is what all the specs are written in (and what ultimately the coils use to fire the plugs).

You can find DVA adaptors from small engine specialty places, usually in the 20-30 buck range - so worth it if you will use it more than a couple of times, but otherwise, any small engine place (motorcycles etc have similar ignitions) can test for you.

And yes, the Mercury switch could be faulty. Simply disconnect it and make sure the lead going to it doesn't ground out anywhere (the Mercury switch and kill switch simply send the ignition to ground and electricity always takes the easiest path to ground - so a wire connection is "easier" than jumping the gap on a sparkplug...)...
 
galamb said:
You can use a regular multi-meter but it requires a DVA adaptor between the meter and the stator.

The DVA acts like a rectifier to convert the AC (which if you measure the AC from the stator gives you a "meaningless" value) to "persistant" DC which is what all the specs are written in (and what ultimately the coils use to fire the plugs).

You can find DVA adaptors from small engine specialty places, usually in the 20-30 buck range - so worth it if you will use it more than a couple of times, but otherwise, any small engine place (motorcycles etc have similar ignitions) can test for you.

And yes, the Mercury switch could be faulty. Simply disconnect it and make sure the lead going to it doesn't ground out anywhere (the Mercury switch and kill switch simply send the ignition to ground and electricity always takes the easiest path to ground - so a wire connection is "easier" than jumping the gap on a sparkplug...)...
Click to expand...

Are there two stators for this motor? and could a bad rectifier have anything to do with it?
 
Depending on the exact model, but you most likely have two stators if the second one is present at all.

One is for ignition - it contains both high and low speed windings (bobbins) that provide all the power that the ignition needs. It does not produce power for charging a battery etc.

A second separate unit, which was an "add on accessory" on many models ONLY produces power for either a regulator (was sold as a "lighting kit") which was used to power the Navigation lights without having a battery OR it fed a rectifier (sold as a "charging kit") which then was wired to the battery for charging (the latter would have been standard on an electric start option from factory).

In either case the charge stator, which is a totally separate unit and the rectifier have "zero" to do with your ignition. If you toast your rectifier and it burns out your charge stator, the ignition stator is not affected at all (unlike other models that have the two stators incorporated into the same unit).

So no, in this particular case it would not be suspect..
 
Yep, that's here (at least the CDI aftermarket equivalent - the OEM stator lists at about 160 bucks).

I have used CDI product many times in the past and am well impressed with it - well made.

Again though, before you drop 120 bucks plus shipping you might want to find a small engine place and chuck the 30 to 60 bucks they want to do a DVA test on the stator.

Ya, you might be out 60 bucks plus the cost of the new stator - but you may save 60 bucks by not replacing a part that still works fine...
 
Ok then, remove the sparkplugs and try pulling it over - see if something seems to be binding/rubbing or is a little seized.

If it pulls over fine, put the plugs back and and "eat some wheaties" :)
 
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