Spare impeller shelf life?

I replaced the raw water pump on my Westerbeke generator last Spring.
After about 160 hrs run time, I replaced the impeller as several fins were severely degraded. I used a spare impeller that the previous owner had on board and seemed in good shape. I carefully picked out any loose fins or rubber and made sure I got all the pieces of the old impeller out. As I pay close attention to water flow from my Generator and main Engine, I am certain there was never any point when it ran dry, or with reduced flow. So I assumed with normal wear and tear, I should proactively replace it every 100 - 120 hrs. I ran the Generator another 20 hrs before pulling the boat for the season. After winterizing the boat, I took the impeller out so it wouldn't sit in antifreeze all winter and I noticed that one of the fins was already starting to tear off. I don't know how old the spare impeller was, but it looked new and was pliable when I put it in and am confident I installed it correctly (and didn't damage it when I removed it). Is there a shelf life for rubber impellers?? Any other thoughts or suggestions. How many hours do you get out of an impeller?

Your post made me search.

A rubber impeller will gradually lose its mechanical properties over time. In this case the manufacturer says 3 years. The impeller will also lose mechanical properties by the number of cycles it goes thru. The manufacturer in this case says 300 hours

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CaptGary said:

I replaced the raw water pump on my Westerbeke generator last Spring.
After about 160 hrs run time, I replaced the impeller as several fins were severely degraded. I used a spare impeller that the previous owner had on board and seemed in good shape. I carefully picked out any loose fins or rubber and made sure I got all the pieces of the old impeller out. As I pay close attention to water flow from my Generator and main Engine, I am certain there was never any point when it ran dry, or with reduced flow. So I assumed with normal wear and tear, I should proactively replace it every 100 - 120 hrs. I ran the Generator another 20 hrs before pulling the boat for the season. After winterizing the boat, I took the impeller out so it wouldn't sit in antifreeze all winter and I noticed that one of the fins was already starting to tear off. I don't know how old the spare impeller was, but it looked new and was pliable when I put it in and am confident I installed it correctly (and didn't damage it when I removed it). Is there a shelf life for rubber impellers?? Any other thoughts or suggestions. How many hours do you get out of an impeller?

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Well, it's early morning but I'll try this one. Soo-Valley's information is useful in establishing outer limits. However, while it gives an impeller life, it doesn't really give guidance on spare impellers and their use.

Also, note, impellers do have significant quality variations.

Our philosophy is as follows. We prefer to always change impellers before they break. We like to do it as routine maintenance at our convenience and not as an emergency repair.

When you keep the spare longer and then make a replacement, you run into what you did. The spare may already be down to half life or 20% life. So, let's say 300 hours or 3 years is the numbers. Then if you use one 300 hours in two years, the replacement you put in is down to a third of it's life.

So, here's our practice. We change annually or sooner if usage dictates. That way we never put in a spare that has been sitting more than a year.

Yes, we do use more impellers than we have to and we don't get maximum mileage and we throw out some "perfectly good" (I put that in parenthesis because none of us can tell how much they've really weakened) impellers. We just consider impellers as cheap compared to all the potential issues. They are not really that well made. Also, we don't want to be out on a rough day trying to pick pieces of an old impeller out and then changing one and every boating law says it will happen at the worst time.

Fact of life rubber impellers die, and can flush rubber hunks inti the cooling system.

Simple solution is a Sendure Y (or similar) style strainer after the impeller pump.

Nice SS screen cleans out is seconds .May have to locate a used unit.

Some folks will vacuum seal spare parts to extend storage life.

I would carefully inspect the impeller pump housing, wear plate, cam and cover plate for damage that might be damaging your impellers. I know you said you monitor the water flow carefully, but perhaps it is periodically sucking air due to a bad hose or seal between the pump and the intake thru hull.

I will tell you life expectancy and shelf life vary a great deal depending on size, manufacturer, and pump model. It's a good idea to limit shelf life with an annual replacement program, and replacing the spare. Some impellers last much longer than others. One of the Waterman in the yard I use has gotten over 2,500 hours on impellers in his Cat 3208. Had another friend go 10 years before replacing them in his 2 Cummins B series (1,500 +/- hours). Alternatively, I've replaced the impeller twice in 5 months in my Kabota generator engine. The Sherwood pump ate the last one in 160 hours.

I added a clear bowl strainer to both my engine and generator, after the raw water pump. It does 2 things. First, it catches the impeller bits and anything too big to go through the heat exchanger tubes. Second, it allows me to check for a failing impeller when I do my engine room checks. Bits in the strainer means I need to change the impeller.



Ted

O C Diver said:

I will tell you life expectancy and shelf life vary a great deal depending on size, manufacturer, and pump model. It's a good idea to limit shelf life with an annual replacement program, and replacing the spare. Some impellers last much longer than others. One of the Waterman in the yard I use has gotten over 2,500 hours on impellers in his Cat 3208. Had another friend go 10 years before replacing them in his 2 Cummins B series (1,500 +/- hours). Alternatively, I've replaced the impeller twice in 5 months in my Kabota generator engine. The Sherwood pump ate the last one in 160 hours.

I added a clear bowl strainer to both my engine and generator, after the raw water pump. It does 2 things. First, it catches the impeller bits and anything too big to go through the heat exchanger tubes. Second, it allows me to check for a failing impeller when I do my engine room checks. Bits in the strainer means I need to change the impeller.

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Ted

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Brilliant idea

And storage conditions also play a role in shelf life.

I found this:
temperature – The storage temperature should be around 25˚C, and products should be stored away from direct sources of heat. Humidity – The storage should be in a dry area. Light – The products should be protected from direct sunlight, UV and artificial light that has a high UV content.

jleonard said:

And storage conditions also play a role in shelf life.

I found this:
temperature – The storage temperature should be around 25˚C, and products should be stored away from direct sources of heat. Humidity – The storage should be in a dry area. Light – The products should be protected from direct sunlight, UV and artificial light that has a high UV content.

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Most plastic and rubber parts will deteriorate if stored at too high a heat. That of course begs the question, what is too high?

When snowbirding to the Palm Springs area over the past 10 years, we have learned, sometimes the hard way, about those plastic and rubber bits on cars and motorhomes.
For example:
-Batteries bought new for the motorhome, that only lasted 18 months, were replaced under warranty, with the vendor commenting that I had been lucky to get over a year, in the heat of the desert. (My boat batteries average around 10 years)
-wipers on the motorhome disintegrated in only a couple of years,
-plastic bits on the car that had been left in a friend's garage over the hot summer had failed, with the shop doing the repairs commenting that heat-related failures of this sort were very common if cars were kept in the heat over the summer, even in closed garages.
-RV dealers claimed they were not allowed to sell motorhomes with tires older than 5 years. Tires that cost up to $1k each. (on my wife's car that was re-tired recently, the old ones were between 15 and 18 years old)

In SW BC, none of these considerations exist. The shelf life of tires, impellers, belts, hoses, is not relevant. When asked, vendors give you the blank stare, not understanding why you would be concerned about deterioration of plastic and rubber bits while on the shelf.

If your boat is kept in a cool climate, that shelf life will be greatly extended when compared with hotter climates.

That YMMV could never be more evident.

The storage temperature should be around 25˚C,

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That is above room temperature.

O C Diver said:

I will tell you life expectancy and shelf life vary a great deal depending on size, manufacturer, and pump model. It's a good idea to limit shelf life with an annual replacement program, and replacing the spare. Some impellers last much longer than others. One of the Waterman in the yard I use has gotten over 2,500 hours on impellers in his Cat 3208. Had another friend go 10 years before replacing them in his 2 Cummins B series (1,500 +/- hours). Alternatively, I've replaced the impeller twice in 5 months in my Kabota generator engine. The Sherwood pump ate the last one in 160 hours.

I added a clear bowl strainer to both my engine and generator, after the raw water pump. It does 2 things. First, it catches the impeller bits and anything too big to go through the heat exchanger tubes. Second, it allows me to check for a failing impeller when I do my engine room checks. Bits in the strainer means I need to change the impeller.



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Ted

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that alone is worth the long hours spent on trawler forum

Thank you!!

jleonard said:

And storage conditions also play a role in shelf life.

I found this:
temperature – The storage temperature should be around 25˚C, and products should be stored away from direct sources of heat. Humidity – The storage should be in a dry area. Light – The products should be protected from direct sunlight, UV and artificial light that has a high UV content.

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I store my rubber spear gun bands in the fridge.

Soo-Valley said:

That is above room temperature.

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That's 77 F and that is the room temperature of my house in Florida when the AC is running.

But yes I usually consider "room temp" to be around 72 F

I really like this idea!!! Thanks!

Rubber parts evaporate out solvents that make them pliable. If you have a vacuum food sealer, it's an ideal way to store impellers and other parts.

FWT said:

Brilliant idea

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On smaller engines

Even better idea on Genset is electric pump - no impellers to change.

ofer said:

that alone is worth the long hours spent on trawler forum

Thank you!!

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I also!