I have a 2006 kawasaki ultra lx waverunner that has vibration at 5000 rpm ?

They are here

http://www.theskiclinic.com/kawasaki-tech.html

Or do you mean engine torque as related to horsepower?
Maximum Torque 152 N·m (15.5 kgf·m, 112.1 ft·lb) @7 250 r/min (rpm)


https://www.google.com/search?q=2011+Kawasaki+Ultra+Jet+Ski.+Torque+specs

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Have you ever heard of RPM roll over? If the engine was allowed to reach it's max RPM under throttle the inertia would cause it to exceed its design max RPM, so it set below that to avoid flying rods and pistons. And yes it is governed.

harmonic engine vibration
as it is still under warranty , take it to a dealer service center and have it fixed

I think the idle, in gear, should be about 750 rpm, definitely not 900. If you are looking at the tachometer, it isn't that accurate visually. a scanner should be connected to get an accurate reading. A little vibration at idle is not abnormal. But you might try adjusting the engine mounts to eliminate it.

what is the answer to this question?

I dont know the answer but my vx deluxe is doing the same thing. Not as bad as yours but 4k rpm idle.....ANyone?

sounds like the cpu is corrupted needs to be re-mapped,  Best to take it in , just ask them to reset it back to default values ,
cheers