new Jabbsco Impellor trashed after 48 hrs solid running

[SteelCruiser]

History - Motor had not run for 12 months:
Started the motor and the sea water shortly stopped coming out the exhaust.
Jabbsco pumps' impellor was no good : the metal shaft had separated from the rubber vanes.
Imstalled new impellor.
When the motor was restarted - again, no water coming form the exhaust.
( the motor ran for less than 5 mins while this was determined )
Water was added to the "strainer" at the top of the loop - the loop that comes from the inlet ( seacock) down below , up to the strainer , then down to the pump with the impellor .
Situation was then good - water coming form exhaust when motor started.

Then motor sailed for 48 hours - with the occasional stop for oil checking etc.

Then the impeller **** itself again. When I took it out, most of the rubber vanes were smashed completely.

Question (s). Did I install this incorrectly perhaps? ( I used the little sachet of lubricant that came with it)

Any other possibilities as to why the impeller became non-operational after such few engine hours?

Have written a separate post about massive fumes from exhaust at same time :
working theory at moment = the Vetus water lock got overheated and perished?
Open to other suggestions , questions / comments

[GILow]

First questions that come to my mind are:

1. What sort of cooling does this engine have? Raw vs fresh. Actually, what make and model, that might help.
2. Have you accounted for all the missing bits of impeller rubber? These will be a problem if they cannot be found.
3. What is the condition of the pump impeller chamber? Scoring or roughness?
4. Was the replacement impeller a genuine Jabsco or a copy? (I have seen some truly awful copies that I threw in the bin, not worth keeping for spares.)

Rather than post on the other thread, I would remark that the waterlok muffler does sound like it might have collapsed internally though the photo you included did not show any signs of overheating or damage. But it was a pretty limited view. There is also a slightly higher chance that the exhaust has collapsed further "downstream". My understanding is that the mufflers are surprisingly robust.


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[GILow]

Finally, sounds like that pump is not self priming. In my very limited experience I have never had this problem, but I may have been fortunate in the way my engines have been setup. However I thought the Jabsco engine pumps could theoretically self prime to one atmosphere (10 meters). So to me sounds more like the pump housing may be damaged.

Edit: here I am talking crap again. Just checked the jabsco manual. 7m is the absolute maximum self priming height. But still, that's a BiG lift and a lot more than I would expect in a sailing boat engine setup.


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[atoll]

could be that the sea cock inlet is partially blocked by barnacles restricting the flow to the pump.

[jimbunyard]

Generally speaking, that the pump worked after installing the new impeller indicates that it is installed correctly.

Was the new impeller from on board 'ship spares', or was it just purchased? Rubber products have a definite shelf life whether they're installed or not, if from on board spares, it could be that the impeller was just old.

As noted previously, any roughness in the housing or cover could be an issue, as well as could be air leaks or restrictions on the suction side.

For locations where there are priming issues, a company called Globe Rubber sells a 'run dry' (15 minute guarantee) impeller that is made of blue Nitrile (I believe) that is available for a fairly large variety of pumps. They are available from many vendors and I know from experience that they work well. There may be other manufacturers of a similar product if you can't find the blue ones in your area...

[tdh1849]

Notice any, "white steam/smoke " coming out of the exhaust when motor sailing ?

[HopCar]

Let's hope Atoll is right. It's the cheapest fix and would explain the problems.

[scottrm612]

The key here is:

( the motor ran for less than 5 mins while this was determined )

The impeller was doomed from the start. They are not meant to run with little or no water. As was stated above, you have a water flow problem. Check the strainer gasket and make sure it is sealing properly.The strainer should be full of water with the engine running. You might need new gaskets.

Also the housing should be inspected or replaced if its plastic. It will have been overheated from the beginning 5 minute run.

[svJasmine]

Scott is right. 5 minutes or less will kill an impeller. There must be a blockage on the way in.

[Sea Angel1]

Hi, white smoke would mean, water in the exhaust, some internal leakage somewhere. Check the oil level. IF fuller than before the water enters your engine and your top engine gasket failed.

[CampDavid]

I would agree that you may have a restrictions or an air leak. REMEMBER the pump sucks to pump and then blows on the other side.

I would also check the cover plate and cam for wear. Those two items can cause the water to not prime properly and then as you run it for 5 minutes without water the impeller is finished.

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[tinkrman69]

Originally Posted by CampDavid

I would agree that you may have a restrictions or an air leak. REMEMBER the pump sucks to pump and then blows on the other side.

I would also check the cover plate and cam for wear. Those two items can cause the water to not prime properly and then as you run it for 5 minutes without water the impeller is finished.

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All of the above posts should checked If the pump is not self priming then you have leakage in the suction side and/or improper clearances in the pump...ie...a worn cover plate. if there is a groove in the cover plate, lap it smooth with some wet-n-dry sand paper on a flat surface, starting with 150 grit and finishing with 220 grit. if the groove is really deep you can lap the other side and reverse the plate. If it was an old spare impeller, don't just assume that was the cause. it's cheaper to check for restrictions and leaks in the intake side, in fact it only cost labor and you get to know the condition and location of all the components in the process. Check all the hoses and accessible locations on the discharge side all the way to the mixing elbow for impeller parts. this would also cause, slow priming and reduced water flow, Causing the impeller to ware faster.

I haven't read your other post. but the title sounds like it should take precedence over this problem. meaning it would be a waste of time and money till you fixed the other problem "first" as if it is a raw water cooled engine a leak in the head gasket to a water passage would cause back pressure and restrict water flow. engine overheating too. Not to mention white snook out the exhaust and water dripping into the cylinder and then into the oil. and eventually water build up in a cylinder and seizure of the engine.

[BlueHeron]

I have had a similar problem before and it turned out to be a obstruction on the raw water thru hull intake.
I suggest removing the hose to the thru hull and see how your water flow is, mine was 90% closed off by some sort of sea creature, the only way we could dislodge it was by using a garden hose with a high pressure nozzle.
I agree with other posts, an impeller should not be ran dry, always make sure you have water flow to pump before starting.

Hope this helps.

[davido]

I,ll pitch of two cents worth in.

I suspect your problem could be a combination of a few different things.

1. You very likely have an air leak somewhere between the impeller and the strainer. The "self priming" works by the impeller moving air out of the line between the impeller blades and the water (sea-level) in the suction hose. As the air is moved out of the hose the normal atmospheric pressure on the water is greater than the reduced air pressure in the hose thereby "pushing" the water toward the pump. Once (or if) the air pressure is reduced adequately to have the water pushed to the impellers then the dynamics change significantly as now the impeller is dealing with a significantly more dense element, water.

As air is far less dense than water, any minor air leakage is adequate to disturb the dynamics of the impeller's attempt to reduce the air pressure and thereby induce water flow. Common sites for leakage include the paper gasket on the seawater pump cover, hose clamps (especially above the waterline), and the seals on the seawater strainer (especially the cover to service the strainer basket). Other less common leaks can include heavily scored surfaces inside the sea water pump, cracked pipe fittings, bad seal in the seawater pump shaft, and an intake hose that is internally collapsing.

2. Any significant obstruction in the suction side of the system makes air leaks (discussed above) more significant. You indicated the motor had not been started in 12 months. You didn't say if those 12 months were spent on the hard or in the water. If it was in the water I would suspect the inlet could be partially clogged with growth. The thru-hull and seacock needs to be scraped clean along with the hull. There could be growth well up inside the seacock and hose, so a long narrow scraper would be best. Complicating this is whether or not you have a strainer grate over the through hull or not and whether or not you have one with a removable grate. AFTER this scraping, if there is a convenient place above the waterline to remove the hose that comes from the seacock you can back flush the line, seacock, and thru-hull with a garden hose and nozzle. You should be able to tell rather easily if it is clean or still blocked.

3. When an impeller spins inside the pump it is synthetic rubber being dragged at a high speed over stainless steel and bronze. This generates heat rather quickly. Fortunately, if everything has been maintained well and is in serviceable condition, water is pushed to the impeller within a few seconds and cools the impeller. Once primed (again the other components in the system are in serviceable condition) the hoses and impeller is sitting in water ready for the next engine start, be it minutes, hours, days, weeks, or months.

Once you destroy an impeller by overheating it, you need to be careful when inserting a new impeller. Frequently there is residue from the impeller melted onto the inside of the pump housing. If you don't remove this residue it can damage the new impeller in a short amount of time. There is good literature available on the web on the rebuild process that discusses this and other issues.

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Bottom line is this is a system with many components that all have to be working well for the system to work well. I think if you should diligently check each component and service/repair/replace each that is not performing at or very near optimal. Don't stop when you find the first problem as you may have multiple items slightly askew generating your issue.

Good luck my friend.

[EveningTide]

Just to let you know, these pumps should self-prime but don't always work as they should. Mine (a Johnson pump) is very subject to air locking. When I change an impeller I must fill the input side hose to the pump and open the top of the strainer and let it overflow to be sure no air is in the system. Then everything is fine. As others have said, running the pump for long without water probably will quickly destroy the impeller. There is lube that comes with a new impeller but who knows how long it will work if water is slow in reaching the pump. I have never destroyed an impeller and have had no problems with water flow since I worked out the above system.