Impellar

My Impellar disintegrated and is blocking the water flow. No water coming out of exhaust .
Where do I look first and then where?

We helped a friend at the river one weekend with this problem, we had a spare impeller for him but his coolant hoses were blocked somewhere.   He spent the entire day taking them off one at a time and clearing out the pieces.   He had a block right at the exhaust manifold connection on one side that was the last found but he had pieces in nearly every hose.   The thermostat housing likely has pieces in it so remove hoses and inspect.   Pull thermostat housing to inspect.   Reverse flush hoses if possible to push pieces out.   Unfortunately the pieces go anywhere the coolant flows.   After seeing how much trouble he had we change our impeller every 2 years in our area.   Seems they fail on the third year for us.