I had picked up an oem impeller from the Yamaha dealer on the way home when the pump wouldn't work. The one installed looked new, but I decided to replace it with the oem one. May be my imagination, but the oem one seemed to fit tighter in the housing. To insure the veins were oriented correctly I put the impeller in the housing first then slid the housing over the shaft. I rotated the shaft so the key would align with the slot on the impeller and it slid right on. Don't know why I never thought to do it that way before. Takes the guess work out of the vanes orientation.I
I'll try it out shortly but it should work.