That's a medium size water pump, if don't wan to remove the broken bolt any time soon, adjust the other 3 bolts tight and apply silicone to the lower water pump countour, let it fully cure for at least 24 hours. Start motor and check if with a proper peeing pressure. There's nothing to lose, only time going to the machine shop, probably returning next day, some days latter and $$$ to save...
If the pump's internal liner is found lightly scratched, can micro polish it to near new condition , wet a large piece of cotton, apply an overdose of toothpaste and rotate it hard in circular motion against the liner till all the micro scratches has been removed to a shiny condition.
If having a dremel rotating tool can perform same procedure with those white cotton feltre bits. Reaconditioned liner and new impeller will pump more water with increased pressure than before and last way longer than if doing nothing. If all water paths, jackets in the entire powerhead are immaculate clean the end result will be much better.
It's entirely up to the OP's which way would want to go.
Happy Boating
