The correct way is to put the impeller on the shaft.----Then make sure the key is driving it.----------Now push the housing down on the impeller while turning the shaft the way the motor turns the shaft.--------The impeller will then go in with the vanes bent correctly.
The impeller is driven by a key !!!----You should stop your assembly work untill you find the key or the hole that the key fits into.-----And you are getting advice from folks who have worked on these motors since 1968 or so.---Did 5 of these motors over this winter !
Okay seem everybody is on the correct track now with the key issue. As far as the impellor vanes turning. If you happen to but the vanes in wrong direction (it happens) they will fix themselves as soon as the engine starts up. So no worry about that if you turned them wrong as the engine turns...
it's a good thing my wife's hands are small. got it back together today now I'm waiting for the longer bolts for the fuel pump? Thanks loads for all your help