He took my crap encrusted pump with all but one of the cover screws broken off and gave me back a nice, clean, functioning bomba de aqua. And he asked for 150 pesos for the work (I gave him 200 because he deserved it and I didn't have change).
So back to the boat and in 15 minutes, I installed the pump and had the diesel purring. I thought I would try spraying the pump with a corrosion inhibitor that's made for battery posts. It's tinted red so you can see where you spray it. We'll see if it will help put off the need to buy a new pump (at about $300 USD).