Voltage spikes on Mariner 115 Hk -93

Mr Olsson is detecting normal "pulses" as we might call " the nature of the beast". I have a 115 Merc, my personal rig of 12 years, which is quite similar. The adapter is not used on my rig as I changed all components to CDI Electronics back in the day when their quality was exceptional. There are already hundreds of hours on this 115 with not a problem except when a brittle oil injection supply line broke off one night while freighting up the lake and the motor froze up. It still runs well, but showing poorer compression after the incident. Next year will overhaul it.
Getting back to the Mariner, I think you will be okay with this primary side surge and as Pappy and Mr. Scott suggest: Let's go fishin'.

OK, thanks a lot. Did Merc give any voltage specification for the test?

In the Mariner/Mercury Outboards Service Manual 1988-1993 for 115 Hk models there are specifications for Voltage readings @ 300 -1000 RPM as well as @ 1000- 4000 RPM for both Stator – Low Speed and Stator High Speed. In this case there is not Adaptor shown in the circuit diagram and there seems to be 2 pair of different windings from the stator low and high speed.

Below test limits are picked up from the manual.

Stator Low speed 160 -385 V (300-1000 RPM) and 270-330 V (270-330V)

Stator high speed 8 -33 V (300-1000 RPM) and 33-205 V (270-330V)

Since I have one winding (feeding the switch box) and an adaptor, the above test specification can’t be applied right on.

So do you have any information concerning the test specifications on the adaptor?

Go here...start at page 2A-6
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Thanks’ a lot for theinformation faztbullet. Since the adaptor component are reducing the AC voltage to a to a upperlimit there must be some kind of voltage regulation components included insidethe adaptor.

I’m really excited to measure the output from theadaptor and compare against specification. I will of course give feedback withthe result (can be little later in spring, it is winter in Sweden now. Perfecttime for research JJ)

I have only done some passive (resistant) measurementson adaptor. The resistance over both the input as well as output to the adaptorshowed high resistance (infinity). If there is/are components inside reducingthe AC input level I would expect some measurable value on at least the inputor outport.

I wonder if a higher voltage could cause any damage onthe remaining components inside the Switch box or primary side of the ignitioncoils?

The explanation that Faztbullet gave as to the source of the voltage spikes (change from N to S poles) sounds more than probable.

You mentioned that you have/had (or had used an O-Scope). You could use that to confirm it was in fact the polar switch.

If you trigger your o-scope to the frequency of the (rpms) of the motor and set your period to a full cycle length - if you have a capture or persistence function on the o-scope (or a fancy new digital one), you should be able to isolate the spike. If it is consistent at/near the zero going positive crossing and the zero going negative crossing that would be consistent with the polar switch.

So as an example if the motor was idling at 1000 rpms (1000 cycles per minute or 16.66666666 cycles per second) the frequency of the AC sinewave would be 16.6666666 hertz. A 60 millisecond trigger with a similar scale on the o-scope would display one complete sinewave. If the trigger corresponded with the positive zero crossing of the wave AND the spike was caused by a polar switch you would see the "spike" captured smack in the middle of the display (or thereabouts) - open your display to the period of 2 cycles and you would see the spike at every zero crossing IF it's is caused by the magnets.

Something to take a look at.

The spikes are normal due to magnets rotating around multiple coils. As the magnet approaches the coil bobbin, it induces a current flow into the bobbin. When the magnet is directly over the bobbin no voltage is produced. When the magnet move away from bobbin in induced current flows the opposite way (AC current). Magols I doubt you have a problem...

Thank’s for your feedback.

The switching between the permanent magnets north and south pole would generate a spikes which have a deterministic behavior and the spikes would most likely appear in-between the moment of the 0 crossing of the sinuous wave AC signal, I agree. The frequency would be (Number of pair of poles) x 16.7 Hz.

The spikes I refer to have a random behavior in time and can be located anywhere on the AC sinewave. I have had problem to find a suitable trigger on the Oscilloscope for this reason (maybe I can try to apply the internal low pass filter on the oscilloscope to capture the high frequency voltage spikeJ ). I suppose I can record the measurements and most likely catch the spikes on the AC sinewave as well.

However on the DC side I have capture the spike by using AC coupling on the oscilloscope and then measured a spike. The result is a signal that has the character of a damped sinuous with a peak of +- 7 V going to 0 and period time of approx. 5 ns .

Based on the high frequency character of the transient my theory is more into a load damp scenario. I.e. from ignition coils which is not shorted by the parallel diodes after ignition. This transient is then transferred back to the stator via the adaptor.

I’m looking forward to make the addition measurements to catch “the voltage spike ghost”.

Good luck with your motor. Every time somebody tells you something you just disregard it and prattle on about what you think the problem is. I have never known anybody to hook an oscilloscope up to an outboard motor and now I know why. I am still in favor of you polishing it to look like a mirror and hang it on the wall.

I have hooked up an oscilloscope to my motor because of 2 reasons.

1. My remaining problem, short random (in time) voltage transients signals are not captured on a standard DVM (Digital Volt Meters) as they are designed to measure RMS (Root Square Mean) values, that is a single value representing an average over series of samples of measurements.
2. I’m un electronic engineer and this instrument (oscilloscope) are standard tools in engineering to make an adequate analyses of electronic signals.

If someone is interested in what a voltage transient is, how they are created, how they can be harmful and methods to suppress thy, below link can be useful to study.

https://www.electronics-tutorials.ws/power/transient-suppression.html.

Good luck with your motor. Seeing as you yourself said the.motor runs fine, I am sure you will be able.to find a problem where there isn't one. I go back to hang it on the wall.

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I congratulate you on finding a problem that has vexed you for a while now your testing protocol is impressive and exacting however it was of no consequence to the operation of the engine to any degree. You are now satisfied that your engine is running properly and we have had a tutorial on electronics testing, I trust that everyone is happy now.

I should add this, it was good of you to give us the "end of the story" results we don't always hear how things turn out.

Yes, thanks for that. Now I know why I really don't trust resistor plugs and I rarely use NGK.

[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]You are welcome!

I think one of the strongest reason and purpose of forums in general is to finalize "the story" with the founding’s. Most people probably don't "reason" in this way instead they think "now problem is solved for me" and that is the most important thing. The spread of knowledge is not that important.

Comment to Swagomaster: No, the voltage spike didn't have any degradation at all of the engine's horsepower, staring and so on. My worries were more related to the eventually secondary harm the spikes could cause my 12 V loads like radar or nav. equipment.

Finally a PS. One other thing I could measure was that after switching off a inductor load (electrical motor like trim tilt or starter motor) voltage spikes are noticed on the oscilloscope as well. This is in good agreement with the physical laws of currents that are momentarily broken across inductive loads. I wonder if the modern starter motors have built-in protection against
this? DS
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Are you an electrical engineer by any chance? I've only seen people in engineering areas that are so obsessed with details, it's part of the training I guess. Aside from that, yes it is to me very valuable to know what eventually fixed an issue, not just for those that tried to help and wondered how much their input contributed to the solution but to others that read the thread later to try to diagnose their problem. Glad you were able to fight it to a finish. Enjoy the water!

My guess is that starter motors would not be effected because while cranking, the spike will easily be absorbed by the giant amperage draw of the starter itself.....and while spinning the afflicted motor, the voltage spike would be ignorable.....if nonexistant. But with delicate electronic gear and running with full output, I share your concern......however, of course your battery/batteries act as a substantial voltage sink. I'm not an electrical engineer, but I helped my family build a couple FM radio stations and a head end for the largest cable TV, broadband w/fibre optics network north of the Twin Cities. My Dad was a student teacher in electrical engineering and later introduced cable TV to Hibbing MN in 1964, then engineered, built, and managed WDIO TV here in Duluth in 1965, 1966......selling investors on his dream, then multiplying their money 6 fold in 18 years. Interest in electronics was instilled in me from a child. I have really enjoyed this post....thanks again, Tim.
PS. You could have also measured the spark gap jump from plugs to ground. My guess is the good plugs may have been able to reach a 7/16" arc while the open plug with failed resistor.....maybe half that arc, say 3/8". Could certify that with my adjustable spark tester but instead clipped between ground and base/body of spark plug.

The difference between electrical as starter and electronics as in microcircuitry are a world apart in how much voltage variation they can tolerate. A 12 volt high amp starter is the 900 lb gorrila and can take a lot of abuse and not even feel it, circuits that run only perhaps 5 volt and milliamps of power are a different animal altogether. Having said that unless the voltage fluctuations are significant the internal circuitry in the device will take care of it, after all how many times have you seen a bad spark plug damage something, the battery soaks up almost all of the ripple. Now if you were to say create a spark when putting the battery cables on the variation is on the wire and the battery can't buffer it, it's not firmly connected and you can expect small components to give up and get smoked.