What happens when you do not look after your outdrive leg water pump impeller

Having got the lower half of this MerCruiser outdrive unit it was in a sorry state 

Full of dirt and other rubbish 

After undoing the bolts and nuts holding down the water pump upper housing found the root cause of the engine cooling problem, the water pump impeller totally U/S little or no blades left behind    

Even the upper housing is U/S as it got hot and as mis-formed itself and so as the lower plate 

Now got the new parts on order should be up and running again