Water (circ) pump failure
 

Anyone ever see or have an impeller fall of a circulation pump? (the one on the engine, almost similar to a car/truck)

Mine did, found by pure chance by spinning the pulley with the belts off and it made a funny noise. Pump was mercruiser and only one season on it. Looked like wasn't brazed on.

I am very tempted to put an automotive one on it, even though I have a new one at $135.

I just put a new circ pump on Friday night. Had just finished replacing thermostats and the thing started howling. The pulley was loose because the shaft has broken in some way. Once I got the pulley off I could see it had been dying a slow death-the weep holes had corroded nearly shut.

Marine ones have stainless impeller , automotive are plain steel. Even if you run in fresh water I would spend the $100 on a marine one, they rarely fail, sounds like you had a goofy defect.

The impellers are actually bronze or cast brass. The old bad one was a OEM merc, and so is the new one. I have both a new Merc and an automotive type on hand.

Just keep in mind that if you still have the reciept that Mercury gives a year on those pumps.

john:D

i just replaced mine , never made a noise but rust made a lil hole in the top and it was pee'ing all over my engine
ebasicpower sold me mine brand new aftermarket for 65 after shipping , hella deal for a marine 454 circulating pump