As posted above, check out the intake side and the pump side...sounds like you got something stuck up there!!
Had the same problem last time out...went close to a public park that has a beach...when I wanted to leave I started to get a vibration so I shut it down and idled to the dock, pulled out the boat and found a plastic kite handle stuck within the discharge side of the pump!! Pulled it out, luckily I didn't see any damage to the wear ring...put the boat back in the water and she went just fine.