Seven years on the same impeller?

[BabaYaga]

Following the recent threads about inferior quality impellers (Johnson) for Beta Marine engines, I have a ”problem” of the opposite kind: Should I put my original Jabsco impeller in for its 7th season?
My 20 hp Beta 722 dates from just before Beta switched from Jabsco to Johnson raw water pumps. Every autumn at layup I do as the engine handbook says: ”Withdraw impeller, inspect for cracks, excessive wear, lost vanes. Replace with new as necessary”.
Now after six years and 340 hours I still have not found any of that. As can be seen in the close-up picture there is some wear on one side of the vane tops, but not excessive as far as I understand. Absolutely no sign of cracks.
So is there any reason I shouldn’t put it back in again?
http://www.ybw.com/forums/images/attach/jpg.gif
http://www.ybw.com/forums/images/attach/jpg.gif

 

[rotrax]

Following the recent threads about inferior quality impellers (Johnson) for Beta Marine engines, I have a ”problem” of the opposite kind: Should I put my original Jabsco impeller in for its 7th season?
My 20 hp Beta 722 dates from just before Beta switched from Jabsco to Johnson raw water pumps. Every autumn at layup I do as the engine handbook says: ”Withdraw impeller, inspect for cracks, excessive wear, lost vanes. Replace with new as necessary”.
Now after six years and 340 hours I still have not found any of that. As can be seen in the close-up picture there is some wear on one side of the vane tops, but not excessive as far as I understand. Absolutely no sign of cracks.
So is there any reason I shouldn’t put it back in again?
http://www.ybw.com/forums/images/attach/jpg.gif
http://www.ybw.com/forums/images/attach/jpg.gif

If it aint broke-dont fix it! Carry a spare and as you have inspected it frequently you know how to change it. 340 hours is not a lot of use and it appears servicable to me.Good luck.

 

[VicMallows]

Only changed my last one after 6yrs and that didn't show any serious deterioration. Stays in all year. I always have spares and mine is easy to change if necessary.

Vic

 

[doug748]

Top work.
I seem to remember that I rarely replaced the Jabsco impeller on my Petter Mini Twin over about 10 years. When I did replace one, it was simply to put a new one in and keep the other as a spare.

 

[WoodyP]

I have replaced every year since the engine was new in 2004, and now have a selection of replacements for "emergencies".
The only time one has gone wrong was when I forgot to turn on the seacock. One went hard, so I chucked it, but the rest look as good as new, however for the cost of a new one have always thought it was good policy to replace before I needed to.

 

[sailorman]

Following the recent threads about inferior quality impellers (Johnson) for Beta Marine engines, I have a ”problem” of the opposite kind: Should I put my original Jabsco impeller in for its 7th season?
My 20 hp Beta 722 dates from just before Beta switched from Jabsco to Johnson raw water pumps. Every autumn at layup I do as the engine handbook says: ”Withdraw impeller, inspect for cracks, excessive wear, lost vanes. Replace with new as necessary”.
Now after six years and 340 hours I still have not found any of that. As can be seen in the close-up picture there is some wear on one side of the vane tops, but not excessive as far as I understand. Absolutely no sign of cracks.
So is there any reason I shouldn’t put it back in again?
http://www.ybw.com/forums/images/attach/jpg.gif
http://www.ybw.com/forums/images/attach/jpg.gif

i have a Yammi 2 T 2hp O/b with the same 30 yr old impellor

 

[theoldsalt]

WoodyP,

I'm with you all the way.

Why risk having an impellor failure when for a few pounds you can start each season with a new one.

Sod's Law dictates an old one will fail at the most inconvenient time when lives could be at risk.

In my book prevention is better than cure.

Do those who wait for an impellor failure to occur before replacing it apply that philosophy to the rest of the boat/engine maintenance? Sounds like bad practice to me.

 

[Ripster]

I have replaced every year since the engine was new in 2004, and now have a selection of replacements for "emergencies".
The only time one has gone wrong was when I forgot to turn on the seacock. One went hard, so I chucked it, but the rest look as good as new, however for the cost of a new one have always thought it was good policy to replace before I needed to.

Yep I am the same, even though I oly do 70ish hrs a season normally on the engines I have (in my case two) the impellers replaced each year regardless to try and rule out any failures as far as poss. Bur I now have 6 perfectly serviceable spares in case of trouble - so its prob not truly needed, just makes me feel better!

 

[fisherman]

Replaced once in 9000 hours. Never had one fail completely, just pump a bit less, find a couple of cracked vanes.

 

[dutyhog]

My 20 hp Beta 722 dates from just before Beta switched from Jabsco to Johnson raw water pumps. Every autumn at layup I do as the engine handbook says: ”Withdraw impeller, inspect for cracks, excessive wear, lost vanes. Replace with new as necessary”.
Now after six years and 340 hours I still have not found any of that.

Our is similar, on a Beta 28hp. We have two impellers, and swap them each year, never seeing any wear or damage after 6 years at an average of about 80 hours per year. On the previous Watermota engine the impeller only needed changing once in 500 miles (but it broke up when in a rough sea round the west of Mull, when it wasn't easy to work on the engine).

Whether to change it every year depends on your attitude to the balance of risk (seems low according to these posts), cost & time (both also fairly low).

 

[theoldsalt]

Fisherman,

Are we all talking about the same type of pump impellor - jabsco as shown in BabaYaga's post and changed only one in 9000 hours?

 

[trapezeartist]

It seems preposterous that an important engine part should only have a life of a year or two. And I suspect it's only an old wive's tale that we have to keep on changing them with such regularity. It makes me wonder how many problems have been created by removing a proven good impeller and either replacing it with a new one with a defect or incorrectly fitting the replacement.

Remember when F1 teams used to spend all Saturday night at a Grand Prix taking their cars to bits and putting them back together? Raceday mechanical retirements ran at about 25%. Then they were made to put the cars into parc ferme after Saturday qually and reliability instantly improved.

 

[fisherman]

Fisherman,

Are we all talking about the same type of pump impellor - jabsco as shown in BabaYaga's post and changed only one in 9000 hours?

Absolutely. I reckon keep the seacock filter good and never run dry. Same for my deckwash Jabsco which is much bigger. If I recall, the smaller engine impeller had a couple of cracks when I changed it.

To be fair, if I had a failure I would simply put the deckhose through the engine, but the only time I had to do that was when the seacock handle failed, in 'off'.

 

[Ricd]

Only changed my last one after 6yrs and that didn't show any serious deterioration. Stays in all year. I always have spares and mine is easy to change if necessary.

Vic

Like wise...only ever changed 1 impeller in 10 years and that was only because I felt maybe I should!! I know others who religiously change it every new season.

 

[neil_s]

It maybe that things change as the water pump gets older and more worn. On my 1977 Bukh (Johnson pump) I have found that an impeller will last two years or maybe a bit more. Failure manifests itself in reluctance of the pump to self - prime the system when starting the engine - although it will run OK once primed. The impeller always looks fine.

Neil

 

[fisherman]

It maybe that things change as the water pump gets older and more worn. On my 1977 Bukh (Johnson pump) I have found that an impeller will last two years or maybe a bit more. Failure manifests itself in reluctance of the pump to self - prime the system when starting the engine - although it will run OK once primed. The impeller always looks fine.

Neil

On a Jabsco that usually indicates that either or both end plates are worn. One is the cover, the other a plate behind the impeller. You can reverse the cover.
AND, my pump is below the waterline, so no priming needed.

 

[Avocet]

WoodyP,

...Sod's Law dictates an old one will fail at the most inconvenient time when lives could be at risk....

.

I think Sod's law could just as easily dictate that the brand new one had a manufacturing defect and fails at an inconvenient time!

That, of course, is the dilemma. I think with many components you get a "bathtub curve" for reliablility, where you get a high number of failures within a very short time (defective manufacture), then the number of failures drops off for a while, and then the number rises again as they get old and worn out.

I'd be interested to see how many impeller failures were on "new" (i.e. less than 1 season old) impellers and how many were on "old" (say, more than 2 seasons old).

Personally, I come down on the "condition monitoring" side of the divide when it comes to maintenance - inspect and replace IF NECESSARY, but not as a matter of course. Current one is about 10 years old but boat has been out of the water for last 4. Whilst out of the water it has been used as a "bilge pump" to empty rainwater every now and then, so it has had to prime through a height of about 3'! In addition it has been run dry a couple of times (housing cover too hot to touch!) and it still works (but I WILL now change it before going back in)!

 

[Scotty_Tradewind]

sounds to me as if Speedseal need to develop a see-through Speedseal, so a good look through the 'spy glass' can give a better idea how things are doing in there. It could then save on gasket, sealant and brass threads. ???

I also suspect that some impeller housings are made/finished better than others and have less friction to do damage ??

 

[BabaYaga]

Thanks all for your input, many interesting views.
I will most likely continue the experiment and use it for another season. And inspect very closely next autumn, of course.
The ”bathtub curve” suggested by Avocet appears very reasonable. But I suppose defective manufacturing is much more difficult to spot than wear and aging.

 

[LadyInBed]

Never had one fail completely, just pump a bit less, find a couple of cracked vanes.

Same here, replaced Jabsco impeller 7 years ago due to two fins starting to split and it's about the same for my Suzuki o/b.