I don't think you should be hitting the rev limiter nearly so much... the pump is coming "unhooked" far too easily. I'd go ahead and pull the pump out and inspect it, take pics of the impeller and post. There should be almost no gap between the impeller blades and the wear ring, it should be a tight fit to slip a business card between them. Your engine sounds like it's doing right, your pump not so much. You don't need to remove the impeller to inspect it, but you do need to get the pump off the hull so you can clearly see the impeller all the way around (and take pics of it perhaps to post). Also look for any foreign objects while you're in there, even a small twig can mess up waterflow thru the pump.
Also what were water conditions like when you did your WOT speed tests? Water that's glassy smooth actually causes drag (almost feels like driving a car with flat tires IMO), water that's overly choppy also causes loss of speed... ideally you want just a little chop to "loosen up" the hull without causing air to enter the pump intake. I doubt water conditions could account for this much speed loss and hitting the rev limiter frequently though.
Ya'll can call it a "dream-o-meter" all you want, but odds are it's not off by more than 1-2 mph at the most... close enough for the vast majority of boaters. Unless it's outright broken it is NOT 6-7 mph off.
ps. What was the speed/performance like before the SC rebuild and new wear ring installed? Did things improve, get worse, or stay about the same after the dealership worked on it?
- Michael
