Seems no matter how much I read up on jets and impellors and sleeves, I had to learn about them the hard way. I recently sent my stainless impeller off to get rebuilt and put in a new sleeve and my spare aluminum impeller on my Merc 100. The boat seemed to fly alot faster and we were skooten up the creek to where I felt we better come off of plane and not damage the aluminum impeller. I shut the engine down and it wouldnt start or turn over. I removed the spark plugs and sprayed WD40 down the 4 cyls and still no movement....we rowed down and long story short is that the impeller and sleeve didnt have enough clearence!! yeah i'm a rockie with the jet thing!