Why don't they make stainless steel impellers?

[ryanerb]

Seems like the biggest problem on any boat motor is the 'rubber' impeller getting 'brittle' and old and 'chunks break off' and they have to be replaced every year. The answer might be SUPER simple, but why don't they make stainless steel impellers so we no longer have to deal with probably the biggest maintenance and problem causing item in boating?

Ryan

 

[Don S]

Re: Why don't they make stainless steel impellers?

The way the pump works is by the vanes flexing open and closed creating the pumping action. Hard to do if the impeller is stainless steel.

See if this helps explain them.

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

The way the pump works is by the vanes flexing open and closed creating the pumping action. Hard to do if the impeller is stainless steel.

See if this helps explain them.

Great point. I wonder if there is some design such as like a jetski pump that uses a stainless impeller to draw the water in instead of this flexing and pumping option. I feel most other types of water pumps for other applications don't use the same design as a boat, (think car water pump) and thus are better off.

 

[Don S]

Re: Why don't they make stainless steel impellers?

There are also marine versions of the automotive water pump. They are known as circulation pumps. They do not produce the suction nor the pressure to do what the raw water pumps are designed to do.
Pumps like the jet pumps would be a lot more expensive and and not sure they would create the suction to operate as the current pumps do. There are some types of pumps that would work, but cost is the biggest concern.
Don't forget, you are also dealing with salt, sand, mud, sea weeds at times, marine growth etc. The pumps all have to deal with those items on a daily basis.

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

There are also marine versions of the automotive water pump. They are known as circulation pumps. They do not produce the suction nor the pressure to do what the raw water pumps are designed to do.
Pumps like the jet pumps would be a lot more expensive and and not sure they would create the suction to operate as the current pumps do. There are some types of pumps that would work, but cost is the biggest concern.
Don't forget, you are also dealing with salt, sand, mud, sea weeds at times, marine growth etc. The pumps all have to deal with those items on a daily basis.

ya, i'm no genius, im sure someone would have come up with something better if there was such a thing.
i guess the suction is pretty strong, amazing a little rubber disc over several feet can create that much suction.

I'm learning, thanks for all the help.

 

[StevNimrod]

Re: Why don't they make stainless steel impellers?

It depends on how you define "better off" and who ends up being better off.

From the perspective of the company, you're going to have to tank a bit of money into R&D and you'll probably have higher input costs (stainless being more expensive than rubber). That means, for a given profit level to remain stable, price must go up. If you want profits to increase (which, from the company's perspective, would be the whole point of this exercise) the price must go up even more. Once you get here, people start complaining. Depsite what people generally think about engineers and how things are designed, a lot gets limited by cost constraints.

From a consumer's standpoint, most impeller failures are caused by accident (think plastic bag covering intakes), abuse (running the engine out of the water without muffs), or neglect (boat sat untouched for years). I, as a consumer, am not sure that I want to get stuck paying more for something that was already adequate under normal usage conditions. Not to mention what might happen to the rest of the cooling system if chunks of stainless are getting circulated as opposed to chunks of rubber. In theory I would like to see certain design improvements when it comes to boats. In practice, I'd be hesistant to pay a premium for a part designed around accident, abuse, and neglect.

In this scenario, the company is likely worse off, as are most of those who perform regular PM.

Point being, almost nobody is better off when $2 is spent solving a $1 problem.

 

[Tahorover]

Re: Why don't they make stainless steel impellers?

My 1946 Chrysler Crown has metal gears in it's water pump and their original and have about 3000 hours on them. . You could use a rotary vane style pump and do away with the rubber.

Pump problems and their repair are big bucks for the industry.

Rotary Vane pump

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

My 1946 Chrysler Crown has metal gears in it's water pump and their original and have about 3000 hours on them. . You could use a rotary vane style pump and do away with the rubber.

Pump problems and their repair are big bucks for the industry.

well good to see someone out there has a metal impeller. ya, i was going to say , so many consumers lose out on the impeller side, and the parts/mechanics benefit. i know they are consumer mistakes, but still, making stuff as idiot proof as we can will help out people. I would pay 200 bucks more for a boat with a longer lasting pump than something with rubber that needs replacing often.

 

[JimS123]

Re: Why don't they make stainless steel impellers?

Industrial positive displacement pumps have a SS impeller and a rubber housing. They last for tens of thousands of hours if they only pump water.

But then again, factories have to work 24/7/365. If they didn't last that long, someone would come along and find a way to make them last. The factory will pay whatever it takes to avoid a shutdown.

On the other hand, boat companies can't make any money unless we schmuks keep putting money into repairing their stuff and since we don't demand longevity we're stuck with it the way it is.

 

[Silvertip]

Re: Why don't they make stainless steel impellers?

Industrial positive displacement pumps have a SS impeller and a rubber housing. They last for tens of thousands of hours if they only pump water.

But then again, factories have to work 24/7/365. If they didn't last that long, someone would come along and find a way to make them last. The factory will pay whatever it takes to avoid a shutdown.

On the other hand, boat companies can't make any money unless we schmuks keep putting money into repairing their stuff and since we don't demand longevity we're stuck with it the way it is.

And just how much do those positive displacement pumps cost? I suspect by the time they would get "marinized" to handle the sand, silt, and muck, and other debris that passes through them the cost of the outboard would go up another couple hundred bucks -- if one is lucky.

 

[Rocky_Road]

Re: Why don't they make stainless steel impellers?

Maybe your question should be: "does someone make a better rubber impeller?"

They do:

Guaranteed to run dry for quite a few minutes without any damage.

Happy boating!

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

Maybe your question should be: "does someone make a better rubber impeller?"

They do:

Guaranteed to run dry for quite a few minutes without any damage.

Happy boating!

and who might the manufacturer be? website? do a LOT of people run these?

I am more than happy to spend extra money on something that isn't as easily damaged, and more importantly, damaging my entire motor

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

And just how much do those positive displacement pumps cost? I suspect by the time they would get "marinized" to handle the sand, silt, and muck, and other debris that passes through them the cost of the outboard would go up another couple hundred bucks -- if one is lucky.

I think in the end, even 500 bucks more would be worth it. 5,000 maybe not. A boat is already thousands and thousands of dollars , what is 500 more bucks for reliability? I wonder if i can retrofit one of these pumps... The ports on my outdrive don't seem large enough to let all that much come through to the sea water pump. A filter with a clear hose might even help with maintaining clean water.

 

[Rocky_Road]

Re: Why don't they make stainless steel impellers?

and who might the manufacturer be? website? do a LOT of people run these?

I am more than happy to spend extra money on something that isn't as easily damaged, and more importantly, damaging my entire motor

Made by Globe...they guarantee that you can run for 15 minutes dry without any problems. Not to mean that they endorse that kind of abuse, but to point out that their composite impeller is that good. Many of us have pulled the lower units because we feared that we may have destroyed our impellers by a momentary lack of water, and this could take that worry out of our minds.

http://www.globecomposite.com/pages/products_impeller

Happy boating!

 

[dwco5051]

Re: Why don't they make stainless steel impellers?

An outboard water pump has to work in all environments. A sliding vane or gear pump does not handle foreign matter well. A little sand or crud will pass right through a rubber impeller pump with little damage but a positive displacement pump with out flexible parts might end up as just a bunch of small pieces.

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

An outboard water pump has to work in all environments. A sliding vane or gear pump does not handle foreign matter well. A little sand or crud will pass right through a rubber impeller pump with little damage but a positive displacement pump with out flexible parts might end up as just a bunch of small pieces.

good point, i wonder if a water filter could help out with this? of course if that filter gets clogged you are back to square one and overheat. haha, we are getting techinical now, but if we had a water flow or pressure gauge we could monitor the clogging issue.

 

[Silvertip]

Re: Why don't they make stainless steel impellers?

good point, i wonder if a water filter could help out with this? of course if that filter gets clogged you are back to square one and overheat. haha, we are getting techinical now, but if we had a water flow or pressure gauge we could monitor the clogging issue.

You apparently don't realize just how much crude passes through a water pump. Next time you back out of your slip note the debris that is stirred up. That crud passes through the engine. If you happen to have a deep water slip that is not as much of an issue, but the vast majority of outboard owners use shallow water slips or ramps. As for the filter, one would likely need to replace it (or clean it) before/after/during every trip. Then that suddenly becomes yet another maintenance item that people will ignore.

 

[TilliamWe]

Re: Why don't they make stainless steel impellers?

Okay, who else is waiting for Ryan to "introduce" us to his great new product? Ryan, impellers in boats cost $28 (Mercruisers) and they last A LOT longer than a year. (Mine went 4+ years in the sandy silty Illinois River) No need to re-invent the wheel, or the pump. Those Globe impellars are great, if you need them. Porblem solved. No need to go looking for a solution to a problem that doesn't really exist.

 

[HT32BSX115]

Re: Why don't they make stainless steel impellers?

Seems like the biggest problem on any boat motor is the 'rubber' impeller getting 'brittle' and old and 'chunks break off' and they have to be replaced every year. The answer might be SUPER simple, but why don't they make stainless steel impellers so we no longer have to deal with probably the biggest maintenance and problem causing item in boating?

Ryan

Howdy,


A rigid metal impeller (of the same size) would not move anywhere near as much water as a flexible rubber impeller because of the way they work.

Rigid-impeller type pumps are centrifugal pumps which not only do not prime well but at very low RPM cannot produce any where near the volume and pressure of a positive displacement flexible-impeller type pump.

The rigid impeller and housing would have to be a lot larger to produce the volumes needed at low RPM/idle and if large enough would produce so much volume and pressure at high RPM, you would need a regulator to slow it down.

There's also the problem with sand and debris or other injestion FOD (foreign object damage) mentioned above.....



Regards,



Rick

 

[ryanerb]

Re: Why don't they make stainless steel impellers?

Okay, who else is waiting for Ryan to "introduce" us to his great new product? Ryan, impellers in boats cost $28 (Mercruisers) and they last A LOT longer than a year. (Mine went 4+ years in the sandy silty Illinois River) No need to re-invent the wheel, or the pump. Those Globe impellars are great, if you need them. Porblem solved. No need to go looking for a solution to a problem that doesn't really exist.

Hi TilliamWe, thanks for the comments. I do agree that the system they got is pretty decent and has been working well for many years. This discussion was just to think out of the box, and think of something better. Thats how most inventions happen, just taking something that already exists and making it better. Not saying I'm going to do it, but just discussing some things around it.