How many GPM does a Bravo water pump flow?
02-20-2003 | 08:12 PM
#21
Registered
Joined: Apr 2001
Posts: 105
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From: Raleigh, NC
The Jabsco pump is a vast improvement over the M/C plastic crap. To improve the Jabsco even more we discovered that by using the mercruiser impeller in the Jabsco pump we had better cooling (by more flow and pressure) at higher speeds. It seems that we picked up about 4-5 psi on the top end runs. The difference is that the mercruiser impeller has one less blade and therefore allows for more volume per pump revolution. We also run Imco or Stainless Marine sea strainers with poppet valves set a little above 2-3 psi cracking pressure so as not to blow the strainer tops or preload the suction side of the pump too much.
02-20-2003 | 09:24 PM
#22
Platinum Member
Joined: Sep 2001
Posts: 5,769
Likes: 151
From: tn
Hudson
Your industrial pumps are not self-priming.
They run centrifugal bronze impellers (like the circulating pump on the front of your motor which lasts eons until the seal goes bad from sitting too long when you don't use the boat often enough).
Centrifugal pumps are long-lasting for sure. They can be run dry for a while without damage and they can generate a decent flow rate and pressure (multi-stage pumps can generate LOTS of pressure).
BUT
THEY DO NOT SELF-PRIME.
Thus the essential difference...
The rubber impeller pump is a positive displacement pump. It will pump air well enough that it will pull water up the feed line into the pump. A centrifugal will NOT do this.
In fact, a centrifugal can lose prime with even a small air pocket in the intake.
ALSO - a centrifugal pump has a given RPM range that it is efficient. They typically don't work all that well speeding up and slowing down. Too slow and the flow can stall. Too fast and they can cavitate in an air pocket.
A rubber impeller pump will pump well at slow speeds, yet at high speeds the vanes flex enough to allow the pump to unload while still pumping fluid.
If there was a superior style of pump for the raw water application, I figure that we could easily find it on the side of a $100,000 MTU V-16 2000hp diesel.
Guess what kind of pump it has on it???
You got it - a greeeeeeaat biiiiiiig version of the Jabsco style rubber impeller pump...
Your industrial pumps are not self-priming.
They run centrifugal bronze impellers (like the circulating pump on the front of your motor which lasts eons until the seal goes bad from sitting too long when you don't use the boat often enough).
Centrifugal pumps are long-lasting for sure. They can be run dry for a while without damage and they can generate a decent flow rate and pressure (multi-stage pumps can generate LOTS of pressure).
BUT
THEY DO NOT SELF-PRIME.
Thus the essential difference...
The rubber impeller pump is a positive displacement pump. It will pump air well enough that it will pull water up the feed line into the pump. A centrifugal will NOT do this.
In fact, a centrifugal can lose prime with even a small air pocket in the intake.
ALSO - a centrifugal pump has a given RPM range that it is efficient. They typically don't work all that well speeding up and slowing down. Too slow and the flow can stall. Too fast and they can cavitate in an air pocket.
A rubber impeller pump will pump well at slow speeds, yet at high speeds the vanes flex enough to allow the pump to unload while still pumping fluid.
If there was a superior style of pump for the raw water application, I figure that we could easily find it on the side of a $100,000 MTU V-16 2000hp diesel.
Guess what kind of pump it has on it???
You got it - a greeeeeeaat biiiiiiig version of the Jabsco style rubber impeller pump...
