Joe,
Was the water continuing to spurt out of the exit port down near the waterline? If not, you have a clog in the system.
If so start by closing the thru-hull to the engine intake. You may not have to, but better to be safe.
Take the cover off the pump in your picture. Check out the impeller. Any missing blades? If so, it probably got sucked down the hose to the heat exchanger. You hafta find the broken piece and get it outta there, if so. While you're in there, put a new impeller on. most chandleries would have a replacement impeller. You may need ring clip pliers to get the ring clip off. You may need a new gasket, too, or maybe you can save the old one.
If a broken off impeller vane went though the hose you need to find it. Most likely, it is in the heat exchanger (HE). You will have to climb in there to disconnect it. It could be in a hose or fitting where there is a bend. I f you have to remove the HE, you can unbolt the end plates to look inside for blockage.
Marine Diesel Direct (Torreson Marine) has some on-line diagrams. Look there to get an idea of what you are looking at.
If it is not the stuff described above, you have to delve into it a bit more. I just outlined the most likely scenario.