Raw water pump impeller sudden failure

[BBill]

Jabsco had a bushed bronze pump (JC-1/2) with two grease caps on both sides of the rubber impeller...mostly designed to lube the drive shaft but turning both caps put grease into the impeller chamber and would aid in priming. The top of the pump chamber also has a screw that can be replaced with a zerk. They still sell the impeller but last I looked they didnt list that pump. You may be able to source one somewhere but vintage is probably 1950s-60s.

[caffel]

All of the above are useful suggestions.
In addition, the inside of the pump housing is not invulnerable to wear and small pieces of abrasive stuff or sharp edges which will take a toll, so it needs careful inspection if not disassembly with each impellor failure/change.

[Statistical]

Originally Posted by skwanderer

The result was the impeller had disintegrated into tiny bits and got lodged in the system, resulting in a costly repair by my diesel mechanic.

It is why I put a cheap metal screen filter after the water pump">raw water pump. Cheap insurance. Impellers can die from water starvation and not all of them are user error.

The irony is that since putting the metal screen in I haven't had an impeller fail yet.

[kapnd]

Originally Posted by Statistical

It is why I put a cheap metal screen filter after the raw water pump. Cheap insurance. Impellers can die from water starvation and not all of them are user error.

The irony is that since putting the metal screen in I haven't had an impeller fail yet.

It would seem logical that all Shredded impeller debris would travel downstream to lodge in the coolers, but many mystery overheats are caused by stray impeller bits trapped on the INTAKE side of the pump.
They can reside between the strainer and pump intake grating without causing any problems, and then one day they decide to jump up and block the pump intake, inevitably when you’re in a critical passage, running at WOT.
For your metal screen filter following the pump, not a bad idea, but be careful not to use a screen finer than your strainer screen.

[gonesail]

so did you replace the impeller after running it dry or not?

[LifesBetterWhenYoureBeating]

Originally Posted by gonesail

so did you replace the impeller after running it dry or not?

Yeah, I forgot to make it explicit but that's why I said the engine ran only 100h since that time I let it ran dry. The whole point is that the new impeller failed with only 100h, but I've concluded it was provably caused by a temporarily clogged intake

[Mintymax]

I had the same issue and the impeller was completely torn apart. I replaced the impeller however I’m getting water leaking from two points of the impeller plate whenever I start the engine with the sea cock open. Do I need a new plate ?

[skipperpete]

Originally Posted by BBill

Wow, this is news to me. Is this some type of aybc code or personally inspired? I've owned many sailboats with fwd facing scoops and never a problem. It seems after 50+ yrs and 1000s of cruising hrs it would have reared its ugly head with at least one of my boats. Can't remember seeing a sailboat with the scoop facing aft. If a fwd facing scoop fills the engine its a pixx poor exhaust design.

Once, the forward facing scoop was not a problem but modern cruising yachts are poking along at much higher speeds, some reaching 15 -20 knots. It‘s worth mentioning that initially a new raw water pump impeller will effectively seal the raw water circuit when the engine is shutdown ( particularly the 12 bladed ones) but once the impeller sheds a few blades or wears the end plates a siphon can occur and if the vent loop is poorly installed, blocked or absent there can be an almost inexplicable engine flooding.