Yeah, someone fired it up without the muffs. If not you, who? Did you
take possession of the boat and tow it off directly after the run-up at
the seller's place? Or later?

I bought the boat immediately after running the engine... hooked it up
to my truck and drove away. I'm not saying it's not the impeller, but
it doesn't make sense that it would die just like that. Like I said,
it was working perfectly just minutes before I drove it home.

So back to oe of my original questions... if I'm not getting water at
the inlet hose to the heat exchanger, can it ONLY be the impeller/
pump, or can anything between the pump and exchanger cause this?

Thanks for your assistance!