I have 30 hp two stroke pull start yamaha outboard motor, the motor starts ok but does not pump water new impeller fitted, is it possible to fit it wrong?

Yam water pumps are clever the offste centre causes the pump vanes to flex during rotation and at low RPM you have a displacement type pump, at high RPM water pressure forces the vanes to flex inwards and the pump becomes centrifugal, you can fit the impellar either way up so you cant fit it wrongly make sure your gaskets are ok and that the delivery pipe to the power haed is not leaking (try a hose on it) also make sure the little woodruff key or on some models the pin through the drive shaft which turns the pump is fitted ok, not much else that can be wrong!