If a implellar goes bad on a sea water pump, what actually happens to the implellar? Is it a visual check?

If it comes apart? Where do the pieces go? Can they restrict the water passages?

The impeller is rubber and the blades come off. Sometimes you can see in the back of the pump through the water hose nipples.
The pieces go to the next restriction in the cooling system-usually the oil cooler and they really can cause a restriction. Look at the pieces you get out and you can tell if you have enoughm if not, FIND THEM!!!!!!!!

If the pieces are in the oil cooler how do you get them out?

Disconnect the hose and backwash the cooler?

Disconnect the seawater inlet line at
the thermostat housing, and backflush
thru the hose you just disconnected.

jt