I've routinely pulled apart gearboxes, and put it in the ultrasonic clearner. Works magic.

But an electric motor, I have not needed to do. Most just need surface cleaning, and the inners are fine. There not enough parts in there to make it worth doing. I usually blow them out with compressed air.

I'm sure it would work, but you would need to use plenty of compressed air to get all the water out of it....

I'm assuming your speaking about the transformer. That's not a good idea.

I clean the wires going into it (via alcohol or another substance). Then i sand down the metal that surrounds the unit. Later i tape off the wires and sides, leaving only the exposed metal; and spray paint it black. Comes out great.

There's no point cleaning the inside of the transformer. It's tightly wound wire with zero moving parts.
If you take it for a dip, good luck getting all the water out of it. And then comes a nice bad short.

The transformers almost never fail. Just get it clean cosmetically and call it a day.