Maytag 24 in. MDB9750AW Dishwasher "black stuff floating washer run" Questions

...black and gungy inside, then this is probably your problem (It's slime mould that seems to love to collect here and jam stuff up). It may be possible to clean it in situ using hot soda or vinegar ...

black impeller (small circular thing with one screw in the middle) then removed the bottom plastic housing. At this point you can see the cutter blade and the channel which will have the junk floating