5KW motor noise

[B0bD]

I have a 5kw water cooled 48V motor with a VEC300 controller, connected to a 14 cell LFP battery, powering a converted 9.9 Evinrude outboard.
It works fine but it is really noisy.
3-4 feet away, under no load, with the engine cover off, I measure up to 90 dB.
This is with the motor disconnected from the outboard motor gearbox.

Is this noise level unusual?

Is it possible for a mistake in the wiring to cause excessive motor noise?

IThe noise drops about 10dB when I put on the heavily insulated engine cover, but even 80 dB is much noisier than I would expect.

Any thoughts or suggestions will be appreciated.

[Corchard]

What sound is it making?  And where is the noise coming from:  electric motor noise, Gear noise, battery noise, water pump noise,Controller noise,...?

I have the air controlled version of that setup and at full speed it is barely above 40 DB.

[B0bD]

sound file attached, running with no load, from zero to about 4500 RPM

The motor is running by itself - water pump off, gearbox disconnected.

With my stethoscope, it sound like the noise is coming from the upper area of the motor ( opposite the output shaft.
Unless there is some way that mis wiring would cause such a noise, I think I'll have to pull apart the motor and check the bearings.
Its out of warranty.

Wonder if anyone has an exploded view of the motor.

[Corchard]

Everything about that recording sounded normal (similar to mine) except the high tinny pitch at ~8 seconds (at maximum RPM.)

You can set the max on the controller to be just below that RPM. Load may help.

[B0bD]

problem it that it peaks at 90 dB.
I built the outboard last year, and used it last summer, despite the noise.
Just as noisy in operation with the prop installed and pushing our pontoon boat.

Decided it needed to get fixed somehow otherwise it is pretty useless.
Mentioning your motor is much quieter helps, at least affirms there is something unusual with mine.
I have wondered if I got the phasing wrong by mis wiring whether that would cause a high motor noise.
Not something I want to experiment with, thought, without some certainty it might be the issue.
The increase in noise at about 4000 rpm is concerning, because that is well within the motors limits.

[Bikemad]

I think it may be under-propped as the original motor is designed to run at 5-6,000 rpm.
I suspect that a larger diameter/pitch prop will be needed to allow the motor to run at a lower speed and produce a lot more thrust.

According to the dynomometer data the HPM48-5000 motor produces its maximum power output @ 3,206 rpm (~6.5kW) and the power output drops significantly as the rpm rises above this figure (~2kW @ 4,000 rpm).

If your motor is reaching 4,000 rpm during normal use it is clearly not producing the power it is supposed to.

A larger diameter/pitch prop should load the motor sufficiently to prevent it from reaching the noisy rpm and produce a much quieter running outboard. 

Alan
 

[B0bD]

It may be under propped for getting maximum output, although max motor speed of 4500 is close to the original engine speed of 5000.
In any case I use it for slow cruises, and I have fooled around with a different prop to see what happens.  Nothing on the noise frot.
The problem is that it is really noisy even at low speeds, whether or not it is under load.

The 90dB mentioned in my initial post is the peak, it hits 80 at about 1/4 speed.
Corchard's comment that his setup is below 40 dB makes me think there is something wrong with my motor, either bearings or electronics.

[B0bD]

Bit of a followup
I took the end plate off, and noticed that the bearing has a bit of fust on the outside.
possibly or probably not an issue but the bearing doesn't look as pristine as is should being sealed in a motor.
There is a side load adjuster and I can get rid of a lot of the noise by increasing the preload, and cna increase the noise by loosening the preload.
The bottom bearing also looks less than fresh so I am going to replace the bearings.

Possibly of use to someone - upper bearing NSK 6304Z, lower (output) bearing NSK 6006Z.  They are commonly available.

I'll report back once I get the new bearings.