Broken vanes from pump impellor..

[NealB]

I've just removed the impellor from the raw water pump.

Of the 13 vanes, ten had completely disintegrated.

Do I need to worry that there was very little debris in the body of the pump? Will the broken bits have been blown through, or could they cause a blockage?

Thanks.

 

[vyv_cox]

A blockage is possible. In a fresh water cooled engine the most likely place for bits to lodge is in the heat exchanger. In a raw water cooled engine it depends upon the route taken but there could be bits in the thermostat, in the injector into the engine, or inside the block. Your engine may have cover plates that will allow you to inspect inside the jacket.

I would inspect the easier possibilities, i.e heat exchanger, thermostat, block entry, but I would wait and see before going in to serious disassembly, as it may not be necessary.

 

[omega2]

you will have to suck it and see, unless you want to take all the pipes and coolers off, generally the bits go through but not always, afater refitting check exhaust outlet immediatly for water, if you feel it is restricted no option but to clean out the system.

 

[omega2]

you will have to suck it and see, unless you want to take all the pipes and coolers off, generally the bits go through but not always, after refitting check exhaust outlet immediatly for water, if you feel it is restricted no option but to clean out the system.

 

[stuey_two]

This is no help to NealB but is it practicable to fit an inline strainer after the impeller to catch any broken off vanes? The problem is not uncommon but the remedial actions proposed seem a bit hit and missas well as tedious.

 

[PeterGibbs]

Most of the vanes missing suggests something radically wrong. The odd vane might go missing in a season - could this impeller have been otherwise in service so long? Or is another agent at work - perhaps clogged ingress of raw seawater laving the pump to run dry, if intermittently. Needs looking at on a whole system basis, I think.

I guess that if the engine has not overheated to date from vane pieces jamming in the waterways, and guessing the vanes have dropped off progressively over time, the system might well be one that can cope with such debris. In which case, dismantling and purging is not indicated. But keeping a close eye on water flow and engine temperature certainly is. Should temperature float up and down without reason, the system should be purged for safety.

PWG

 

[Anonymous]

I've had that happen to me. Our generator water stopped flowing (classic dry-exhaust sound and shut down long before the electrics could detect it) and found all the vanes but one had gone. I just put a new one in and all is well. I have run it for around 30 hours since then. I think it's just the way these things fail unless you change them regularly. I tend not to change them too soon as a good one can last almost indefinitely. My engine impeller is rated for 500 hours.

BTW - I think it is a bad idea to put the old impeller back in if you take it out for the winter. Might as well put a new one in as they can get damaged removing them. I leave mine in all year round.

 

[TonyS]

Have just changed my impeller. One vane was missing and that was stuck, half blocking the outlet to the pump. The previous impeller lost 2 vanes and was changed in Benodet last summer when the water output was noticeably less. Those 2 vanes were found at the entry to the heat exchanger and were removed through the rubber sleeve with a pair of long nosed pliers having felt them with my fingertip.

 

[pollygonforty]

nearly funny story, on passage across aegean,overheating problem.upon investigation impellor broken, one vein missing,can feel vein blocking pipe try to remove vein withlittle finger and manage to get finger trapped!!! engine still hot of course and finger swelling by the moment,call SWMBO and tell her to set course on broad reach and please get me some cold water , fairy liquid , KY whatever! eventually decide only course of action is PANIC! rip finger out causing quite severe laceration.Moral of the story of course never put your finger where it does'nt belong /forums/images/graemlins/blush.gif

 

[Anonymous]

Four of us with lost vanes and 238 reads to date. We are all following this thread and have viewed several times, so let's guess 75 forum members. Let's assume that only 1/3 of members actually post so that gives us effectively 12 in 75 or 16% of us who have direct experience of lost vanes.

Makes you realise how common the problem is - surely engines ought to be designed to pass the vanes without blockage? My Fischer Panda with Kubota engine seems to have passed the vanes. Which engines did not?

 

[Roberto]

I also found a few missing vanes in the impeller (on ap erkins 4108): I could find all the missing pieces in the short pipe between the salt water pump outlet and the exchanger inlet; I put all the pieces together to theoretically rebuild the impeller, just to check that no pieces were lost inside the exchanger...
the exchanger inside copper pipes have such a small diametre that I suppose if a piece of impeller can pass through them, then it will easily reach the exhaust... just an impression

fw

 

[pollygonforty]

come on Lemain lets not get too serious, you know impellers are not forever,renew them every year! its not abad policy

 

[Anonymous]

[ QUOTE ]
come on Lemain lets not get too serious, you know impellers are not forever,renew them every year! its not abad policy

[/ QUOTE ]Infant mortality is not unknown, and wear is low. So after a year or so of use the impeller is still fine and has proved itself not to have manufacturing defects so why change it for one that might have? Do you change your car tyres every year even if they are not worn? Or your alternator belt? All your hoses? Your clutch? etc. So why change the impeller?

 

[Topcat47]

I replace mine every year. Only once have I had a broken vane (in an old Volvo MD1b) Raw or fresh water cooled, the cost of an impeller or two is tiny compared with that of a seized engine.

 

[Anonymous]

[ QUOTE ]
I replace mine every year. Only once have I had a broken vane (in an old Volvo MD1b) Raw or fresh water cooled, the cost of an impeller or two is tiny compared with that of a seized engine.

[/ QUOTE ]The cost of the impeller is trivial. I am suggesting that changing the impeller long before the rated service interval might be counter-productive since a certain proportion of impellers will be defective from the factory. Those that have survived, say, 50 hours are perhaps likely to survive for 500 (or whatever the manufacturer states for that engine). Also, remember, that for many engines changing the impeller is very difficult and introduces the risk of poor workmanship during the change; yet another risk.

 

[john_morris_uk]

To add to the stats, our engine impellor had one vane missing when I removed it at the end of last season. On my list of 'to do' jobs is taking the end off the heat exchanger to fish out the bit. On our Volvo 2040 the bits always gets stuck against the end of the pipe stack in the heat exhanger. Fortunately its fairly easy (but messy) to take the end of the heat exchanger off and clean it out.

 

[Phoenix of Hamble]

It does however, provide another justification for a 'speed seal' impellor cover, allowing more regular inspection as part of the standard pre-sail checks, or on a monthly basis.......

 

[vyv_cox]

I fully agree. Some impellers seem to fail at a very early age, whereas others last for years. I inspect mine every year, deflecting all vanes in both directions and examining them carefully with a small magnifying glass (on my Swiss Army knife). If they are not cracked I replace them.

The only rider to this is that flank wear can cause the pump not to suck when dry. If this becomes apparent I replace the impeller as a matter of course.

 

[jimbaerselman]

Classic cause of broken vanes is overheating - in my case due to starting the engine with the salt water inlet cock turned off /forums/images/graemlins/blush.gif .

Almost certainly, a number of pieces will be trapped in the heat exchanger (they were) blocking off or reducing the flow in a percentage of pipes. Luckily, it was easy to remove the exchanger and clear it. I didn't think of re-assembling the vane to check for missing bits though!