Something is way wrong with your pump! Or maybe your tach is bad? But you should be seeing around 4000-4500 I'm guessing, I don't know how much HP your making but it would take over 600HP to spin a "tight" pump 6k. I had a 12wj with a B impeller that i spun 5000 all day. It was thirty years old, very beat. I sucked up some rocks one day and then ran almost 6000! I had rocks stuck in the impeller and broke off vanes in the bowlAn energizer kit from Tom at jet boat performance put me at 4700 with an A. This is when I discovered that jet boats launch hard! My old pump was junk! How is your boat out of the hole? Does it feel like it has a slipping clutch or does it hook up? First thing to do is pull the clean out cover and look for junk stuck in the impeller. Also inspect the impeller for damage while your in there. Did you replace the wear ring? Come back with any info you may have there are a lot of sharp helpful people lurking here that will have more to add