Motorguide "Whine"

[Harvey Manfrenjensenden]

Hello all, well this one is really throwing me through a loop. The only way I can describe it is through a link to a YouTube video I uploaded so you can hear it. It's a bit louder on video than in reality, but you can still hear it from 20' away, and when it's in water it resonates through the head unit even louder.

Here's the video:

https://youtu.be/E3lzkik-L9w

- 2010 Motorguide Pro Series 75# 24v (I'm ready and waiting for the "shoulda bought a Minn Kota" comments haha)
- this video is taken without the prop on
- commutator is clean, no flatspots although there is one pin-sized chip in it, but I bought this second hand and for all I know it's always been there (chip doesn't look new by any stretch)
- brushes are clean and smooth
- magnets are intact, no cracks and are firmly in place within the unit
- I've tried a very thin coating of grease in the bushings at both end caps
- I've tried rotating both end caps, and although it changes the tone slightly, it doesn't do much
- the shaft is straight, no detectable fluctuation or wobble
- the inside of the unit and the electronics are very clean
- batteries are just shy of two months old, optima blue-tops fully charged
- motor is wired to the console, 6ga wire to a plug with 6ga adapter (the wires both at the battery and at the plug are quite cool to the touch. After about 5 minutes of runtime out of the water, the lower unit gets pretty warm to the touch, but I'm guessing that is somewhat normal)

It started doing this about 2 weeks ago, after putting a new prop on it. Prior to the Machete III, it had a Hydrazilla Hacker on there, which was a much bigger and heavier prop, so I'm not sure if the motor developed a load memory due to the prior resistance. It was on there when I bought it a few years ago, I don't know how long it's been on there in total. That being said, it does this now with or without a prop on it...

Has anyone here come across something like this who can think of something I might have missed, or have a better idea than what I've already tried? And guys, if I even thought I could afford a new Minn Kota or something else right now, trust me... I would have done it instead of posting a long winded violin playing sob story

 

[gm280]

Harvey, I have now tried two different times and can't view the video because it states the video is not available now. So I can't hear what your trolling motor is actually doing. :noidea:

 

[Harvey Manfrenjensenden]

Harvey, I have now tried two different times and can't view the video because it states the video is not available now. So I can't hear what your trolling motor is actually doing. :noidea:

Man, what the heck? Well thanks a bunch for letting me know! Try this:

https://youtu.be/E3Izkik-L9w

 

[gm280]

Man, what the heck? Well thanks a bunch for letting me know! Try this:

https://youtu.be/E3Izkik-L9w

Okay Harvey, I was able to see and hear your trolling motor this time around. I have to ask, does this trolling motor have a maximizer on it, as in a PWM circuit? Because it sounds like switching circuit noise to me. If this were a AC motor I would say it is the AC switching current noise associated with such motors. But being a DC setup, it could be the PWM circuit frequency you are hearing. But not being there and trying things myself, that is about the best I can say. If this is a PWM circuit, it could be in need of a O'scope check out to see if there is any change in the pulse. JMHO!

 

[Harvey Manfrenjensenden]

Okay Harvey, I was able to see and hear your trolling motor this time around. I have to ask, does this trolling motor have a maximizer on it, as in a PWM circuit? Because it sounds like switching circuit noise to me. If this were a AC motor I would say it is the AC switching current noise associated with such motors. But being a DC setup, it could be the PWM circuit frequency you are hearing. But not being there and trying things myself, that is about the best I can say. If this is a PWM circuit, it could be in need of a O'scope check out to see if there is any change in the pulse. JMHO!

Ooh... gm280 you went a little bit over my head with that one, but based on a little bit of research to try and understand what you are referencing, I'm going to say "no". I believe it is bone stock, with the variable 5 speed foot controller containing constant/momentary/high-bypass. (TM S/N 950010310)

I hope that I was able to answer your question halfway intelligently, but let's just say for discussion purposes that one was added by the prior owner, and I have no idea what it is or what it would look like, is there a place on my TM that I could look that would allow me to answer your question more definitively? I am guessing it would be under the foot pedal, but even if a digitizer was added I don't think I would know what to look for.

Sorry about this, I really hate asking questions then finding out I know much less than the little bit I already thought I knew :facepalm:

 

[gm280]

Ooh... gm280 you went a little bit over my head with that one, but based on a little bit of research to try and understand what you are referencing, I'm going to say "no". I believe it is bone stock, with the variable 5 speed foot controller containing constant/momentary/high-bypass. (TM S/N 950010310)

I hope that I was able to answer your question halfway intelligently, but let's just say for discussion purposes that one was added by the prior owner, and I have no idea what it is or what it would look like, is there a place on my TM that I could look that would allow me to answer your question more definitively? I am guessing it would be under the foot pedal, but even if a digitizer was added I don't think I would know what to look for.

Sorry about this, I really hate asking questions then finding out I know much less than the little bit I already thought I knew :facepalm:

Obviously it doesn't have such a circuit or it would state something to that effect on the head or foot units. However, let me explain what PWM (commonly called a Digitizer or Maximizer) circuit is and does for future interest.

On some models of trolling motors the factory uses a circuit that literally turns the current/voltage "on" and "off" very fast going to the trolling motor in a fashion to allow the motor to work, but using a lot less battery supply or capability therefore extending the battery life. If you think about turning any circuit on and off so fast that it looks like it is on all the time (as least to the actual motor in this case), you save battery power when it is in the "off" state. And being able to adjust that "on" to "off" state is called a Pulse Width Modulation circuit (PWM). And if you think about turning the motor "off" for a longer period of time then it is "on", the motor runs slower. AND vice verse, if you turn the motor "on" longer then it is "off", then the motor runs faster. So it would have a frequency to that type of circuit. Sometimes, depending on the frequency (the number of on / off cycles) they use, can make switching noises when it is turning on and off. And that was what I was asking about. So I guess we can eliminate such a circuit for that possibility now.

It could be an opened coil winding in the motor and in effect making that same switching noise. Have you noticed any less capability from the trolling motor when this noise started? Since there are no other circuits involved, it has to be in the foot section. Could be a dead armature pad or pads making that switching noise. But that is only my uneducated guess not being there and testing things. :noidea:

 

[Harvey Manfrenjensenden]

Obviously it doesn't have such a circuit or it would state something to that effect on the head or foot units. However, let me explain what PWM (commonly called a Digitizer or Maximizer) circuit is and does for future interest.

On some models of trolling motors the factory uses a circuit that literally turns the current/voltage "on" and "off" very fast going to the trolling motor in a fashion to allow the motor to work, but using a lot less battery supply or capability therefore extending the battery life. If you think about turning any circuit on and off so fast that it looks like it is on all the time (as least to the actual motor in this case), you save battery power when it is in the "off" state. And being able to adjust that "on" to "off" state is called a Pulse Width Modulation circuit (PWM). And if you think about turning the motor "off" for a longer period of time then it is "on", the motor runs slower. AND vice verse, if you turn the motor "on" longer then it is "off", then the motor runs faster. So it would have a frequency to that type of circuit. Sometimes, depending on the frequency (the number of on / off cycles) they use, can make switching noises when it is turning on and off. And that was what I was asking about. So I guess we can eliminate such a circuit for that possibility now.

It could be an opened coil winding in the motor and in effect making that same switching noise. Have you noticed any less capability from the trolling motor when this noise started? Since there are no other circuits involved, it has to be in the foot section. Could be a dead armature pad or pads making that switching noise. But that is only my uneducated guess not being there and testing things. :noidea:

Thank you very much for that, I really appreciate the time you put into providing me with some education on the subject!

Regarding TM performance, since I put in new batteries, and removed the original 12/24 10ga wiring and replaced it with 6a and a new console plug, it's pulling my boat better than it ever has. In retrospect, I do think it may have been making this sound in an unpronounced manner before, which is to say that prior to this the prop sound covered it up, and I took it as simply the sound of a quintessential electric motor, but since performing this work it has become significantly more prevalent.

I could probably Google this, but you appear to be quite knowledgeable on the subject so I'm going to go ahead and ask you, is there a manner in which I can test the armature and/or commutator with a multi-meter to prove/disprove this theory? Speculating, I think it would be difficult since those parts don't necessarily hold energy until it's received through the brush contact and even at that, they are spinning at a high rate of speed... hmm.

***EDIT***

Scratch that last question, my apologies... I'm watching a tutorial on how to check this right now. I will perform this test when I get home from work today, and follow up with you shortly thereafter!

 

[Harvey Manfrenjensenden]

One more thing I should have included in my initial posting, the sound does increase/decrease when alternating between speeds on the foot pedal . Not sure if that's a relevant factor in what this is or not.

 

[gm280]

One more thing I should have included in my initial posting, the sound does increase/decrease when alternating between speeds on the foot pedal . Not sure if that's a relevant factor in what this is or not.

Do those resistance tests and post back. Depending how the armature is wired to the commutator, if one or more wire loops are opened, it could cause a noise. But until you know for certain it all is merely speculation at best. When you do open up the foot, look for other things that could be the noise a well. Like anything that could be hitting a spinning prop output shaft. Even a bearing can be pitted enough to cause noise. So don't rule out anything. Do post back though. I am not really interested.

 

[Harvey Manfrenjensenden]

Do those resistance tests and post back. Depending how the armature is wired to the commutator, if one or more wire loops are opened, it could cause a noise. But until you know for certain it all is merely speculation at best. When you do open up the foot, look for other things that could be the noise a well. Like anything that could be hitting a spinning prop output shaft. Even a bearing can be pitted enough to cause noise. So don't rule out anything. Do post back though. I am not really interested.

Will do, but your last two sentences are really confusing hahaha

 

[Harvey Manfrenjensenden]

Wow. Just wow. SMDH. I want to preface this with a quick story.

My dad, well... father in law has been a heavy equipment/vehicle mechanic his entire life, starting from a very young age. Everything I know about mechanics and repair I know from him. Any task we undertook, he would always say the same thing, "start with the simple explanation first". Me, I'm a land surveyor by trade, and I tend to overthink things in a majorly way, usually to my detriment. Well, he's visiting from Utah, today in fact and while I had the armature out he was hanging out with me in the garage and the 1st thing he did was run his fingers across the armature shaft(s). Low and behold, an imperfection in the shaft. I looked at the shafts the first time I had it out, and you couldn't really see it but when you ran your fingers across the shaft perpendicular to the shaft direction, you could feel it, about 3/8" long almost like a razor cut in the shaft but thinner.

I polished it down starting at 400 grit and ending at 1000 grit Emory paper and viola. It's as quiet as can be.

I'm 38 years old, and I haven't truly "learned" a damn thing about common sense and how to properly apply the concept of K.I.S.S.

The continuity check came back just fine btw... no signs of shorts or breaks. Of course I did this prior to dad coming out...