On a recent survey of a vertical pump motor, I obsevered in peakview, 2x line frequency and multiples of this frequecy. There was no other sugnificant amplitudes in the spectrum.
Could this mean there is a possibility of corona discharge at the peak of the AC wave, or some other electrical phenomona?
The motor is rated at 460 volts and the amp draw is even and less than nameplate. This motor also runs hotter than it's sister motor which is right next to the motor in question. Both motors are the same and pump the same fluids

How much hotter is the motor than the other one?
What are the amplitudes of the vibration readings you are seeing?

Are you seeing any side bands around the 2X line frequencies?

Its pure case of stator air gap variation where insulation resistance is varying.
Please check the same may be it needs electrical overhaul.