Raw water pump - a design flaw?
06-16-2011, 02:00 PM
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Raw water pump - a design flaw?
Greetings,
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
06-16-2011, 02:13 PM
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Fixx
Greetings,
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
look up cp perfoemance and look under sea pumps,,their you will find a ss gousing for your bravo sea pump..if you have a alpha then the gen2 has a ss housing and the older alphas have a plastic one with a ss liner..
06-16-2011, 02:32 PM
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your confused! a steel pump on the front of the engine is called a circulation pump which circulates the water in the cooling system..the other pump is called a sea pump which brings fresh water to the cooling system and will add pressure to the system,how ever they do make a stainless steel housing that goes on a sea pump bur your going to be stuck with a rubber impeller to create the suction and pressure..
look up cp perfoemance and look under sea pumps,,their you will find a ss gousing for your bravo sea pump..if you have a alpha then the gen2 has a ss housing and the older alphas have a plastic one with a ss liner..
look up cp perfoemance and look under sea pumps,,their you will find a ss gousing for your bravo sea pump..if you have a alpha then the gen2 has a ss housing and the older alphas have a plastic one with a ss liner..
Yeah, that SS sea pump you pointed me to at CC Performance is exactly what I was thinking of. Wish I'd known about it before I bought this plastic crap. Next year that's going in for sure.
Thanks for the tip!
S
06-16-2011, 02:49 PM
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Greetings,
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
I'm starting this new thread after a some comments on a previous thread about my raw water pump got me thinking.
On the engine the water pump is made of metal. They're durable, they last for years and years and years. You don't even think about replacing one until you see water weeping out or it's obvious it's not working.
But raw water pumps on marine engines are a rubber impeller inside of a plastic housing (at least in sport boats). In my opinion, they're highly unreliable. You need to replace it at least every season. If it fails, it can cause big problems. And there's always a fear of burning it if you don't have good water supply.
It's such a simple part, yet so important. Why are they made so cheaply and fragile? Seems like if you have steel raw water pumps, you wouldn't have to even think about it for years upon years. And I gather manufacturers are still using crappy plastic/rubber raw water pumps (I always have old boats).
Is there such a thing as a high performance raw water pump? One that has steel parts instead of plastic and rubber, that doesn't have to be replaced every season. If there's not, I think I have my next business idea. A raw water pump that lasts years, not one or two seasons. I replace mine yearly now, just because of all of the problems I've had when one fails. I realize they aren't terribly expensive, and not a huge hassle to replace... but wouldn't it be nice to not even have to think about it?
First, the design utilizing a rubber impeller surrounded by a housing that is eccentric allows for a pumping action that has the benefit of high suction as well as high volume; it's a variable volume pump design in which when the vane sweeps along its arc from output to intake the volume is increasing and thus this lowers the pressure dramatically which creates a very effective vaccuum once the vane reaches the intake port. It's how its able to cope with raising water from below your engine and fight the head pressure or raising water. This is also why its so quickly self-priming. Alternative pumps (rigid designs) do not lend themselves to suction, rather they only create positive pressure on the output side.
And secondly, since most all boats require a steady supply from the waters beneath your boat, you will undoubtedly end up ingesting debris, sand, sea critters, etc. These will tear up a water pump in a hurry. The rubber impeller serves as a sort of sacrificial element in the system so that you can control and mitigate the failure of the entire system to simply the impeller. Imagine is it were all hardened steel components dealing with debris ingestion. Instead of losing only impellers you'd be losing entire housings, pulleys, belts, etc. in the event of a complete pump lock-up. Something's got to give.
Frankly, I don't mind it at all. I change mine once a season and I can do both motors in less than an hour.
Last edited by CigDaze; 06-16-2011 at 02:55 PM.
06-16-2011, 02:55 PM
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It blows me away how much of an absolute goldmine of fantastic information this forum is. I wish I'd thought of coming here before now. It's also a little intimidating when I realize how much I really don't know (and thought I did).
Thanks!
Thanks!
06-16-2011, 02:58 PM
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06-16-2011, 03:22 PM
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The design is twofold, and it's hardly flawed.
First, the design utilizing a rubber impeller surrounded by a housing that is eccentric allows for a pumping action that has the benefit of high suction as well as high volume; it's a variable volume pump design in which when the vane sweeps along its arc from output to intake the volume is increasing and thus this lowers the pressure dramatically which creates a very effective vaccuum once the vane reaches the intake port. It's how its able to cope with raising water from below your engine and fight the head pressure or raising water. This is also why its so quickly self-priming. Alternative pumps (rigid designs) do not lend themselves to suction, rather they only create positive pressure on the output side.
And secondly, since most all boats require a steady supply from the waters beneath your boat, you will undoubtedly end up ingesting debris, sand, sea critters, etc. These will tear up a water pump in a hurry. The rubber impeller serves as a sort of sacrificial element in the system so that you can control and mitigate the failure of the entire system to simply the impeller. Imagine is it were all hardened steel components dealing with debris ingestion. Instead of losing only impellers you'd be losing entire housings, pulleys, belts, etc. in the event of a complete pump lock-up. Something's got to give.
Frankly, I don't mind it at all. I change mine once a season and I can do both motors in less than an hour.
First, the design utilizing a rubber impeller surrounded by a housing that is eccentric allows for a pumping action that has the benefit of high suction as well as high volume; it's a variable volume pump design in which when the vane sweeps along its arc from output to intake the volume is increasing and thus this lowers the pressure dramatically which creates a very effective vaccuum once the vane reaches the intake port. It's how its able to cope with raising water from below your engine and fight the head pressure or raising water. This is also why its so quickly self-priming. Alternative pumps (rigid designs) do not lend themselves to suction, rather they only create positive pressure on the output side.
And secondly, since most all boats require a steady supply from the waters beneath your boat, you will undoubtedly end up ingesting debris, sand, sea critters, etc. These will tear up a water pump in a hurry. The rubber impeller serves as a sort of sacrificial element in the system so that you can control and mitigate the failure of the entire system to simply the impeller. Imagine is it were all hardened steel components dealing with debris ingestion. Instead of losing only impellers you'd be losing entire housings, pulleys, belts, etc. in the event of a complete pump lock-up. Something's got to give.
Frankly, I don't mind it at all. I change mine once a season and I can do both motors in less than an hour.
Great answer!
06-22-2011, 06:15 AM
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The design is twofold, and it's hardly flawed.
First, the design utilizing a rubber impeller surrounded by a housing that is eccentric allows for a pumping action that has the benefit of high suction as well as high volume; it's a variable volume pump design in which when the vane sweeps along its arc from output to intake the volume is increasing and thus this lowers the pressure dramatically which creates a very effective vaccuum once the vane reaches the intake port. It's how its able to cope with raising water from below your engine and fight the head pressure or raising water. This is also why its so quickly self-priming. Alternative pumps (rigid designs) do not lend themselves to suction, rather they only create positive pressure on the output side.
And secondly, since most all boats require a steady supply from the waters beneath your boat, you will undoubtedly end up ingesting debris, sand, sea critters, etc. These will tear up a water pump in a hurry. The rubber impeller serves as a sort of sacrificial element in the system so that you can control and mitigate the failure of the entire system to simply the impeller. Imagine is it were all hardened steel components dealing with debris ingestion. Instead of losing only impellers you'd be losing entire housings, pulleys, belts, etc. in the event of a complete pump lock-up. Something's got to give.
Frankly, I don't mind it at all. I change mine once a season and I can do both motors in less than an hour.
First, the design utilizing a rubber impeller surrounded by a housing that is eccentric allows for a pumping action that has the benefit of high suction as well as high volume; it's a variable volume pump design in which when the vane sweeps along its arc from output to intake the volume is increasing and thus this lowers the pressure dramatically which creates a very effective vaccuum once the vane reaches the intake port. It's how its able to cope with raising water from below your engine and fight the head pressure or raising water. This is also why its so quickly self-priming. Alternative pumps (rigid designs) do not lend themselves to suction, rather they only create positive pressure on the output side.
And secondly, since most all boats require a steady supply from the waters beneath your boat, you will undoubtedly end up ingesting debris, sand, sea critters, etc. These will tear up a water pump in a hurry. The rubber impeller serves as a sort of sacrificial element in the system so that you can control and mitigate the failure of the entire system to simply the impeller. Imagine is it were all hardened steel components dealing with debris ingestion. Instead of losing only impellers you'd be losing entire housings, pulleys, belts, etc. in the event of a complete pump lock-up. Something's got to give.
Frankly, I don't mind it at all. I change mine once a season and I can do both motors in less than an hour.
06-22-2011, 06:51 AM
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My engines have plastic housings, and I never replaced the housing, only the impeller. Then a small piece of one of the housings cracked and came loose inside the assembly. This instantly shredded the impeller and sent all of the little tiny pieces of rubber into the oil cooler, plugging it up. Whatever got through the oil cooler likely made its way into the engine. I now replace housings every year. And since I've discovered the metal housings, next year they get replaced with stainless. That one incident caused me a huge amount of headache.
