Jabsco Raw Water Pump Impeller Failure

[IOLANI]

Firing the engines for the first time this season. Starboard runs without issues. Port engine I had running for a couple minutes and realized I had little to no flow through the strainer ( I could still see the pink antifreeze in it). Thru hull is in wide open position. Shut it down. Engine barely got warm 84 degrees at the freeze plugs. Pulled the raw water pump cover to find the impeller had begun to disintegrate. This is surprising since it was replaced last year. It then made the trip from Fla to NJ without issue and ran cool the rest of last season. Anyway I managed to get the impeller out and have a spare but I’m concerned that the broken off bits of impeller are gone somewhere. Probably enough material for several vanes. I pulled the hose to the intercooler and found nothing. I have no idea if the impeller was coming apart gradually since last year or it all just happened at once at startup. Where would the broken bits of rubber tend to collect ? Do I need to be concerned about them?
Also. The spare impellers on board are still in the box and pliable but I have no idea of their age. Ok to use or best to just buy new ?

My next concern will be for the new impeller...I know these are supposed to be self priming but should I try to pour some water into the upper housing...there are two caps almost look like bleeder caps one on the supply side and one on the housing to the intercooler. I plan on greasing it with the appropriate lube.

 

[Pascal]

You need to find the pieces down stream usually at the heat exchanger inlet.

After splashing or an impeller change I ALWAYS touch the impeller cover as soon as I start the engine to make sure it stays cool. If it feels warm and getting warmer then the pump hasn’t primed. Yes impeller was water pump should self prime but over the years I ve had a couple which did not. Feeling the cover will save the new impeller. Failure to prime is often caused by suction leak.

 

[rwaldrop13]

Another contributing factor is how old the impeller is - Even a "new one" off the shelf may have sat for a while and you don't know what condition it is in. I stored my spares by vacuum-sealing them (The Admiral has a food-saver) and a sharpie to date/label the bag. Plan on reverse-flushing the lines to backwash impeller debris out.

 

[ageless]

spray it with cooking oil or dishwashing soap for that first fire lubrication

 

[IOLANI]

Thanks for all the advice. Live and learn I guess. I never expected a year old impeller to come apart . Like I said it may have been slowly disintegrating since last season and the winter layover finished it.
I'm a bit concerned about trying to retrieve all the missing bits of rubber. What about disconnecting at the heat exchanger and backflushing to the pump with a garden hose ?
Is there any kind of screen inside the intercooler or trans/fuel cooler that would catch the bits or are they free flowing / wide open passageways inside ?

 

[Captain Ralph]

What about disconnecting at the heat exchanger and backflushing to the pump with a garden hose ?

What engines do you have?

 

[IOLANI]

What engines do you have?

Ralph they are 8v92ti

 

[Captain Ralph]

Ralph they are 8v92ti

Raw water has two paths beyond the raw water pump on the TIs,
Raw water splits between the inter-cooler and thru the fuel cooler, before the engine heat exchanger. The inter-cooler has small water tubes that clog easily. The fuel cooler is wide open to just in case the IT clogs up.
Then the debris collects up in the main HE.
So, you have a few hard to get to places to clear grass and impellers bits.
The good news; it takes a lot to block these coolers and HEs.
I'm hoping your clutches are cooled from the engine coolant and not another raw water path after the pump,, before the main HE.

So, There is no easy back flush with a water hose.
How bad was the loss of material from the impeller? Is in not rite there in the pump or out-let neck?

THE issue; As we have discussed with storing spare pumps with the impellers installed, A raw pump on the back of an engine for a while is another example. Impellers take a set sitting after a while. Never to be trusted again.
New impellers to start the season in a hard lesson to be reminded of, the hard way..

 

[IOLANI]

Raw water has two paths beyond the raw water pump on the TIs,
Raw water splits between the inter-cooler and thru the fuel cooler, before the engine heat exchanger. The inter-cooler has small water tubes that clog easily. The fuel cooler is wide open to just in case the IT clogs up.
Then the debris collects up in the main HE.
So, you have a few hard to get to places to clear grass and impellers bits.
The good news; it takes a lot to block these coolers and HEs.
I'm hoping your clutches are cooled from the engine coolant and not another raw water path after the pump,, before the main HE.

So, There is no easy back flush with a water hose.
How bad was the loss of material from the impeller? Is in not rite there in the pump or out-let neck?

THE issue; As we have discussed with storing spare pumps with the impellers installed, A raw pump on the back of an engine for a while is another example. Impellers take a set sitting after a while. Never to be trusted again.
New impellers to start the season in a hard lesson to be reminded of, the hard way..

My raw water pump flows out directly through the intercooler and then onto the trans/fuel cooler.

So its a 12 Blade impeller I'd say there's enough combined material missing to make up 3 full blades. Have no idea if it fell apart in little crumbs over time or in big chunks upon startup. Since there was no water flow upon startup I would have expected the chunks to be lodged right there within the housing or in the outlet tube bolted to the exit port but they were clean. That leads me suspect the pump had slowly been disintegrating for a while and the chunks could be anywhere downstream by now.
The engine temps were fine when I put her away last fall and I watch them like a hawk.

As to your other question it looks like I have one cooler with 4 ports that handles both the fuel and the trans cooling.

So at the risk of repeating myself would it be a waste of time to backflush and see if I catch any debris ?

If I want to peek inside those intercoolers do those intercoolers use gaskets or O-rings to seal the components together ?

 

[rwaldrop13]

spray it with cooking oil or dishwashing soap for that first fire lubrication

I can't find the post (and it may have come from an old DD guy in our marina) use the dish soap. Cooking oil aerosol may cause issues, dish soap is as close to neutral as you'll find.

 

[bostonhatteras]

Try this next time. Take out the pencil zinc at the raw water pump and screw in a fitting that has a taper pipe thread for pump side and garden hose 3/4" straight thread that you'll attach your hose to. let the hose run as you start the engines. you can leave hose running or shut off the hose and if the engine is pumping water youll know it quickly as the jabsco will pump far more water than the garden hose, however youll always have enough water to keep from burning up the impeller. .

 

[IOLANI]

Thanks for all the replies. I do not see a zinc anode in the housing but I'll have a closer look and update soon...

 

[IOLANI]

So after installing a brand new Jabsco impeller with the included grease , priming the hoses with water/Dawn solution it cranked over and started pumping immediately and with good force. This model pump actually has two bleeder caps at it highest point. My theory is that when the impeller was replaced last year by the PO they used one of the "in the box" spares on board. The only problem is the spares are probably 10 years old or more. When I felt how soft and pliable the new impeller was I realized those spares need to be tossed as they are stiff with age.
I never did find some of the small bits and pieces of missing impeller. This is a mystery because 100% of the water that exits the pump goes directly through the intercooler and a cross section of that assembly shows it would be virtually impossible for any of it to pass beyond that unless the pieces were ground as fine as powder. I even backflushed the intercooler with some washing machine socks on the other side to catch any bits and there were none. I'll monitor the plumbing and coolers for a while with a heat gun just to be sure nothing starts to get warmer than usual.

It looks as if this pump design does not employ a zinc of any type. I did however find a loose wire which appears to be a separate ground and which looks as though it may have been hooked to a cover bolt at one time. Not sure why the pump would be bonded unless they felt the gaskets could insulate it from the block..?

 

[bostonhatteras]

It looks as if this pump design does not employ a zinc of any type. I did however find a loose wire which appears to be a separate ground and which looks as though it may have been hooked to a cover bolt at one time. Not sure why the pump would be bonded unless they felt the gaskets could insulate it from the block..?

The tach signal generators can be grounded to pump cover sometimes

 

[IOLANI]

The tach signal generators can be grounded to pump cover sometimes

Tachs are working fine but I'll check thanks.