help no foward after h2o anstall

[buck lee]

got a 3.0 mercruiser alpha drive, everything was fine before impeller install.after i put new water pump in i must have messed up thee fhift linkage,before taking apart shifter was in foward, tried to make sure inside shafts were alingned properly,when i look at the back of the where the shift tabs are it looks like it points foward and backi did have to move prop. to get shat to line up for drive to go back together what did i do wrong ????? all help appreciated. Buck