Low blue wire stator voltage

Sunfish12

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Feb 6, 2011
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260
I have a 1988 Mercury 90, 3 cylinder, I have 90 volts peak at idle and 140 volts revved to 2k. The book says I should have 200-300 volts at all times. Is there anything to check before I buy a new stator. I recently replaced the switch box with a used one. I had no spark on 3rd cylinder. All cylinders fire but runs a little rough for my taste. Thanks
 

ajgraz

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Mar 1, 2010
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1,858
Re: Low blue wire stator voltage

Are you checking that with a DVM or a regular voltmeter?
 

Sunfish12

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Re: Low blue wire stator voltage

Dvm with peak hold. Stator tested bad. Just wishful thinking on my part.
 
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kjspylite

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Jul 2, 2010
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Re: Low blue wire stator voltage

You need to check it with a DVA. I'm not versed in electrical theory, however, I believe without a Direct Votage Adapter (DVA), a multimeter can not capture the peak volts reading necessary to diagnose an ignition system. Basically, they are too slow to ready the quick pulses of volts. Its like reading your outlet at your house. Without the DVA, you would read 120, even with "peak hold". With a DVA you would ready around 170. Experts can detail why this is so (RMS, Sine Waves, and other electrical theory), but I do know a DVA is required when reading volts on an outboard.
 

CharlieB

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Apr 10, 2007
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Re: Low blue wire stator voltage

You either mis-read the book, or you do not have a factory manual.

The stator has TWO sets of ignition coils, low and hi speed, voltage on the hi speed coilsl IS low at idle and climbs with RPM, while voltage on the low speed coils is high at idle and drops with RPM.

120 at 2000 isn't necessarily a bad stator, as the transistion from lo to hi speed coils occurs in the 2 - 3000 area.

The ignition module requires 200 to 300 volts to operate, starting, idling at the low end of the range and increading with RPM.

Are you having a problem with the motor?

Download the free Ignition Troubleshooting Guide from CDIElectonics, look for the link in their support section.

Their guide will direct you where, and how, to test any ignition problem.

Repost with symptoms and we will help guide you further.
 

Sunfish12

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Re: Low blue wire stator voltage

I'm using the manual on (1manual.com/mercury) which I thought was the Mercury manual.
I checked CDIElectronics, it states, and I'm assuming these readings are at idle, 180-400volts. I'm reading 89volts at idle on blue wire.
It says 25-100volts for red, I'm getting 47volts.
But as I said I'm using a new meter with a peak HOLD button. Is Kj correct in saying this meter won't work correctly.
CharlieB, every so often I get bog right from idle then smooths out and goes.
Thanks.
Edit: Any book or online info gives me different specs for this engine, very frustrating.
 
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CharlieB

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Apr 10, 2007
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5,617
Re: Low blue wire stator voltage

An off idle bog is more likely a lean idle mixture.

Load on a two stroke determines idle mixture required for acceleration. A motor that runs great, then an extra person or another fulled cooler, and the motor bogs on take off.

When it begins to bog, 'bump' the key (choke) to richen the mixture. If that improves the condition then open the idle mixture screws (CCW) just the width of their screwdriver blade slot. Repeat as needed to perfection.

If this is a new change to a motor that has always run fine then it may be a sign that the carbs are getting dirty and need cleaning.

What is your WOT RPM? A weak hi speed stator will limit RPM much like an seriously over-propped motor.

A weak low side on a stator has serious starting problems.

If your motor starts, idles, and carries the load to an acceptable RPM, leave the ignition alone for now.
 
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Sunfish12

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Re: Low blue wire stator voltage

Top end runs great with 5400rpm's. It starts great, I just cleaned the carbs thinking that was the problem. I will bump the choke/ idle screw check. Thanks Charlie
Full disassembly of carbs, and they did look spotless, did a full cleaning
 
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Sunfish12

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Feb 6, 2011
Messages
260
Re: Low blue wire stator voltage

I tested the stator with a DVA and it looks good. I found water intrusion on plugs. I think it's the exhaust jacket. I'll pull it soon. Thanks
 

j_martin

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Sep 22, 2006
Messages
7,474
Re: Low blue wire stator voltage

I tested the stator with a DVA and it looks good. I found water intrusion on plugs. I think it's the exhaust jacket. I'll pull it soon. Thanks

As you may have noticed, holding the peak RMS voltage (peak hold) and measuring instantaneous peak voltage (DVA) are two different animals.

The first measures heat value, and the second is a rectifier/integrator circuit.
 
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