I changed my impellar because of low water pressure sensor going off, now I can't get any water to flow except for when I use my factory wash outs in the hull. I backflushed the engine several times with no luck. Everything was fine untill I replaced the impellar. Any ideas 496 mag h.o.

Did you put the hoses back on the pump the same way they came off??? They might be reversed.

What condition was the pump housing and cover in? If they have any scoring, they won't prime or won't pump well. It's not uncommon, pump is a piss poor design... Brass housing with no wear sleeve or wear plates in the impeller cavity. Unfortunately, the usual fix is a whole new pump. Do a search on the subject, it's been discussed here plenty.

i would think you still have blockage from the outdrive to the raw water pump<<<

If the top plate is wore. Lay it up on a disk sander and grind it smooth. That resolved my issue. Nothing you can really do with the bottom on the cavity of the pump. Unless you get a rebuild kit.