Why is my raw water impeller failing so often?

[Rich Stidger]

Spring commissioning 2011-

At 2010 layup, I believed my raw water pump on my Westerbeke generator was just fine. However at startup yesterday, there was no water flow. Impeller inspection revealed that two blades had broken and were gone.

This failed impeller was installed on 7/20/2010 and had only 69 hours on it. The previous impeller had 245 hours on it when I replaced it last year.

The entire pump was replaced on 9/13/2007, so it has about 450 hours on it total. The shaft was tight with no discernible play so I don't suspect bad bearings. No pump leaks at all.

So what is going on here?

 

[Dan Johnson]

Rich...

Who's make is the impeller? I remember reading some time back that one of the alternative to the engine manufacturer's products had a production problem in that there were premature failures and spun centers. Could be your problem.

If you're using the engine/pump mfgr's product, all bets are off. Let us know what you ultimately find out.

 

[Amos Cape]

On my outboard motor this year I had to replace my impeller twice. The problem was that I had a parcel block. After that was cleared all work great. I hope yours is that simple.

 

[kloudie1]

I don't guess we can blame the BP oil spill..??
Just guessing without being able to look at the piece parts, Rich.. Could have been a bad impeller (materials not formulated or cured correctly by manufacturer) Temporary blockage at the raw water inlet, something temporarily stuck in pump (we took some fish remnants out of a buddy's thermostat the other day).. Probably merits a look at the entrance of the heat exchanger for blades and possibly what caused them to fail?? Eccentric in the pump good and tight and presents a smooth entry and exit for the deflecting blade?? Dunno .. interesting though.

 

[Maine Sail]

Spring commissioning 2011-

At 2010 layup, I believed my raw water pump on my Westerbeke generator was just fine. However at startup yesterday, there was no water flow. Impeller inspection revealed that two blades had broken and were gone.

This failed impeller was installed on 7/20/2010 and had only 69 hours on it. The previous impeller had 245 hours on it when I replaced it last year.

The entire pump was replaced on 9/13/2007, so it has about 450 hours on it total. The shaft was tight with no discernible play so I don't suspect bad bearings. No pump leaks at all.

So what is going on here?

Rich,

That is not out of the ordinary for those pumps. The Johnson 810-B1 is the replacement impeller I use and it too lasts about a season. I have tried the Globe impellers and they are worse. For the $19.00 and five minutes to swap it out I don't let it get to me much. Ours was new in the spring last season, as it always is, and when it came out in November one blade was nearly broken free but still hanging by a thread.

These Johnson pumps don't like air or plugging in the intake and will throw and impeller vane fairly quickly..

I find if you buy "fresh stock" from a dealer who turns them over quickly, like Hamilton Marine, they tend to last longer than if they sit in your parts collection for two years before installation.

 

[RAD]

Last summer on the first long motoring trip I too blew an impeller on my Westerbeke 30 and that only had a few hours on it....it did come from the spare parts box and that was my first thought (age) after looking at the pump and seeing stains on the outside I had second thoughts and replaced the whole pump cause a week later we were leaving on a vacation, I still have that old pump and I'm thinking maybe its good? and I always change the impeller every other year maybe it should be every year?

 

[Tom Metzger]

I find if you buy "fresh stock" from a dealer who turns them over quickly, like Hamilton Marine, they tend to last longer than if they sit in your parts collection for two years before installation.

MS - Am I to assume from this that you don't carry a spare? Or throw the spare away periodically?

Being in fresh water, my spare impeller sits for years before use, and then lasts for many years in use.

 

[seadaddler]

Me Too

Must be bad luck or what else it could be I don't dare say but my panda went through about 3 impellers real fast about a year or 2 ago and I was so mad because replacing them is no easy thing to do and dropping the wing nuts was so common and had to order more replacements when the wing nuts fall down and can't find them again,but just this past holiday weekend the strainer for the Gen got clogged with sea grass and the Gen shut it's self off and hard to believe the impeller was good and has been running OK so go figure maybe they made these better.
Nick

 

[Scott T-Bird]

Mystified by these little impellers ....

I had some seaweed in my strainer this spring and after unclogging, I still found that the impeller was failed. Replaced it once again. I had to replace it last year. I've replaced these little buggers 6 times in 8 seasons. I've never yet been able to find any discernable difference between one that goes bad and a brand new one. No defects, no loss of flexibility ... nothing that I can see and I've had the guys at the yard look at them too and they are puzzled just like me. Mind you, I have the only sail boat with a diesel engine on the entire lake so they don't have much experience with anything other than power boats. They say that changing an impeller is not frequent and they do A LOT of boats every year.

I've even taken saved a bad one on a few occassions and tried to re-use it just to see if it would work (since I couldn't see any visible difference) and sure enough it don't work once I've pulled it out. I keep at least 2 spares on board at all times.

I've changed the impeller twice in 24 years on my V-8 Mercruiser ski boat in 24 years with a lot more hours than my little 1GM. That's 3 impellers in 24 years (and the first time was when I buried the intake in mud somehow). What gives?

 

[Steve Dion]

Rich: You may also think about trying the new SpeedSeal. They put teflon pads in the pump. I don't know if these really work or not, but it makes changing out the impeller easier even if they don't last any longer!

 

[Rich Stidger]

Some answers-

Looking at my maintenance records, the original impeller in my 2007 new pump went 245 hours and I changed it before a cruise to Maine last year. The replacement impeller that just failed with 69 hours was a Westerbeke genuine part but it was purchased in 2005. It is the Johnson 810-B-1 impeller. So the pump has a total of 314 hours on it.

I have not clogged the strainer for sure and have not air-locked the pump to the best of my knowledge.

When I replaced this impeller, the shaft was snug in the bearings, no sign of leaks, and the cam was secure. I never found the two blades, but I passed a cable tie into the intake and output of the pump and felt nothing, so I think the pieces got pushed into the heat exchanger. Access is a real problem for both impeller changing and getting the cover off the end of the heat exchanger. I have good flow that looks to be perfectly normal in volume, so I doubt the pieces are causing any restriction in the heat exchanger.

In the past I have used older impellers with no correlation to shortened life, but age of the impeller has occurred to me also.

The only other anomaly is that this new Westerbeke pump uses a different drive pin than the older pumps. Consequently the older impellers need to have the drive pin replaced before they can be installed. I can't see how re-using a drive pin would affect the impeller life as the impeller is exactly the same size and the pin is merely the drive from the slot in the shaft. See the pix below for the new and old pumps, the new and old drive pin (the old drive pin had threads the entire length), and a modified old drive pin filed down to fit the new pump shaft. The newest impellers I bought were not Westerbeke but Johnson branded.

Seadaddler- I went through a bunch of impellers "real fast" myself with the old pump back in early 2006-2007. The cause turned out to be bad bearing in the old pump that allowed the shaft to wobble and that was death to the impeller. Could that have been your problem?

 

[Maine Sail]

MS - Am I to assume from this that you don't carry a spare? Or throw the spare away periodically?

Being in fresh water, my spare impeller sits for years before use, and then lasts for many years in use.

I do carry spares but they are always less than 1 year old from time of purchase. Hamilton goes through the 810-B1 impellers very rapidly so they are turning those impellers often. My spare from the season before becomes my new spring installed impeller and the new one becomes my spare. I also have some impellers that came out in fine shape that I coated in 303 as back ups to the back up.

Some pump impellers seem immune to sitting while others like the 810-B1 from Johnson tend to not do so well.

 

[Steve Dion]

It really does not make any difference if you purchase a replacement OEM part or a third party replacement. The major difference is if the parts were made properly or NOT.

Yanmar had this problem several years ago with the vulcanization on the hubs breaking down. This was on the Yanmar OEM impellers. The point being it can happen to the best of them.

 

[Maine Sail]

It really does not make any difference if you purchase a replacement OEM part or a third party replacement. The major difference is if the parts were made properly or NOT.

Yanmar had this problem several years ago with the vulcanization on the hubs breaking down. This was on the Yanmar OEM impellers. The point being it can happen to the best of them.

The OEM impeller from Westerbeke is just a re-boxed Johnson 810-B1 with the Johnson part number molded right into the rubber hub.. You can pay more from Westebeke or just buy it direct from Johnson as they made the pump and the impeller anyway. Of course the pump was built to Westerbeke specs so you can't buy a replacement pump from them, or the re-build kit, but you can buy the impeller.

I put a Globe in this spring to see if they can redeem themselves in my eyes. The last few Globe impellers I used were horrible and worse than the Johnson impellers, but that is not saying much. Of course at nearly double the cost of the Johnson impeller the Globes ought to have double the life...right...? Hopefully Globe has their issues straightened out but I'll know in a few months...

 

[Scott B]

Ya, the "OEM" Yanmar I buy has Johnson embossed into the side of the impeller. Up here tho, best I can find is $30, although the local marina I paid $51 couple years back........

 

[Rich M]

While taking the Yanmar class last year a suggestion was made to store the spare impeller in virgin olive oil. The explanation was that maintains lubrication and is not petroleum based. FWIW.

 

[Sam Salter]

Not sure if this is relevant, you might stay in the water all year.
But I have a sailing season and the lake freezes in the winter.
When I lay up the boat, I pull the impeller so the vanes don't sit all winter compressed against the housing.
I don't get impeller failures.