How true.....
How true Robin....the debates are sometimes how we are able to come up with answers.....now I also see one of your points Robin. Yes, the circuit has to be open for start, but after starting, if you manually open that circuit, then you should be able to get unlimite rpm.
Posting pictures of what your talking about is the best way for us to understand what your seeing. I can tell you though, you shouldn't see anything out of the ordinary from your intake grates through the impeller, the stator, or through the nozzle.
The issue with the motor running the way it does, may be attributed to a water leak. Have you read your plugs?
Try this. Start the motor. Let it run without water. You have a minute or so before it gets hot. See how the motor runs with no water connected to it. You will be o.k....if by some chance, you run it to long, the continuous beeper will sound to let you know your hot......shut it down right away.
Now, with that done, did the engine run good? Or did it run crappy the same why. If it ran good, that means water is getting into your engine.
Post a pix, let us know how the engine runs without water. Just be aware, you can run for short periods of time with no water.....just not for extended periods of time. But this will be long enough to let you listen to the engine and find out if this may be a problem.
Good luck, let us know what you find out.
Oh, and like Robin said, under normal conditions, the engines idle is limited to 3000 rpm. In the water, the torque on the shaft, will lower it to about 1000.