A wear ring is a lot like a clutch in a car. If it's slipping, you'll get a very poor hole shot. As you approach top end, you'll notice it's not as powerful as a like equipped Ski. Change the wear ring and look for a damaged impeller. You may have a new one, but a bad wear ring will alow shitty pieces to float through the wear ring and possibly damage the impeller. Look at the carbon seal while you have it apart. If there's ANY question about the carbon seal, just replace it. If you're in there already, it's pretty cheap practice to replace it.