Bilge Pump in a Bucket

[Simi 60]

Why not install one of these on the prop shaft?
https://www.fastflowpump.com/bilge-pump

as long as the engine is running, it's pumping, air, water, sludge, trash at 800 rpm, that's 4800 gallons per hour with an 8 foot lift head. No other pump is available at anywhere near the price. I think they start at $700 and go up. All you have to do is make a bracket to hold the outer shell of the pump. Everything splits in half so you don't have to drop the prop shaft to install it. Assemble the vane on the shaft and bolt the two halves of the outer pump shell around the pump vane. Make a bracket to hold the shell so nothing moves and the vane can't hit the pump housing. Plumb up the drain line and you're good to go. As long as the engine(s) are running, you can probably save the boat.

For boats with hydraulic systems, they have hydraulic slush/mud pumps as well

I'm not affiliated with these folks at all, but am a believer...

Mentioned before but the maths doesn't work for some.

We run at 1150rpm with 4.5:1 reduction gearbox.
That means the shaft spins at 250 rpm
Not fast enough to do anything.

To get the minimum 600rpm on their specs we would need to run at approx 2750rpm
That's 1000rpm more than the engine is capable of running.

 

[Capt Ray]

I just changed my order for the 2" / 4700 GPH pump moving to the 3700 GPH version with 1.5" hose. The hose is easier to find! ((And will take up less room to store!))

 

[Capt Ray]

I just changed my order for the 2" / 4700 GPH pump moving to the 3700 GPH version with 1.5" hose. The hose is easier to find! ((And will take up less room to store!))

Just found this... easy to store... both 1.5" and 2" available.

 

[rslifkin]

Just found this... easy to store... both 1.5" and 2" available.

Don't use collapsible hose with a 12v centrifugal bilge pump. You'll lose a ton of flow from the extra backpressure as it tries to expand the hose. Those pumps don't produce much output pressure, they just move a lot of water at low pressure.

 

[dhays]

Why not install one of these on the prop shaft?
https://www.fastflowpump.com/bilge-pump

as long as the engine is running, it's pumping, air, water, sludge, trash at 800 rpm, that's 4800 gallons per hour with an 8 foot lift head. No other pump is available at anywhere near the price. I think they start at $700 and go up. All you have to do is make a bracket to hold the outer shell of the pump. Everything splits in half so you don't have to drop the prop shaft to install it. Assemble the vane on the shaft and bolt the two halves of the outer pump shell around the pump vane. Make a bracket to hold the shell so nothing moves and the vane can't hit the pump housing. Plumb up the drain line and you're good to go. As long as the engine(s) are running, you can probably save the boat.

yeah, I mentioned these back in post #35. I'd love to have one on my boat and likely will eventually get around to doing it. It isn't a panacea; the has to be running, the prop shaft has to be turning, etc.. but I like the fact that the pump is ALWAYS running as long as the boat is in gear. In an emergency while underway, it provides immediate pumping.

 

[Simi 60]

yeah, I mentioned these back in post #35. I'd love to have one on my boat and likely will eventually get around to doing it. It isn't a panacea; the has to be running, the prop shaft has to be turning, etc.. but I like the fact that the pump is ALWAYS running as long as the boat is in gear. In an emergency while underway, it provides immediate pumping.

What reduction is your gearbox?
How many RPM does your shaft turn???

 

[stubones99]

Mentioned before but the maths doesn't work for some.

We run at 1150rpm with 4.5:1 reduction gearbox.
That means the shaft spins at 250 rpm
Not fast enough to do anything.

To get the minimum 600rpm on their specs we would need to run at approx 2750rpm
That's 1000rpm more than the engine is capable of running.

aren't you running long stroke engines?
Most modern engines are 2.x-3.x to 1 ratios and swing a smaller prop than yours.

In your case, perhaps hydraulic would be better. Or Engine mounted...

 

[slowgoesit]

Thanks for sharing this video. I have always carried a smaller 1" version aboard. However, I think he makes the case for having a larger capacity one aboard now that we traverse in 39 footer.

I remember visiting a boat years ago whose intake to the engine cooling system had a plumbed in Y-valve above the through hull fitting. From the Y-valve, a pipe went down to 1-2" above the bottom of bilge. In an emergency 'taking on water' situation, one's own engine/seawater pump could save the day for the cost of some plumbing and some forethought. I have not bothered to do this to our new-to-us Mainship 390.

But, I'd be interested if anyone else on the forum has ever seen or heard of this.

My first boat, a 34' Monk had a similar setup. It was for the exhaust/cooling/muffling pump. End of pipe had a screen over it so it would be less likely to clog from debris. Estimated the pump was probably 1200 to 2000 gph. Not a lot, but it's something, as long as the engine is running, just one 90 degree valve diverts the intake. Along with the two Rule 400 gph, the Rule 1200 gph, and the Rule 2000 gph, the two larger ones on higher mounted floats, and also switchable from steering station, I think I was okay.

 

[psneeld]

Don't use collapsible hose with a 12v centrifugal bilge pump. You'll lose a ton of flow from the extra backpressure as it tries to expand the hose. Those pumps don't produce much output pressure, they just move a lot of water at low pressure.

Correct in my opinion of running those type pumps with that type hose on hundreds of salvage jobs....OK if high pumping capacity is not required or if the head is low and the hose run is straight and cant kink ( rare on bigger boats).

As to engine raw water intakes being used....depends on the engine pump flow and what rpms you will be running at. Weather and boat speed can reduce the max flow by a lot so engines like Lehmans may not pump much at all. The concept is popular, but not always practical other than " more help" but not a primary dewatering pump.

 

[rslifkin]

As to engine raw water intakes being used....depends on the engine pump flow and what rpms you will be running at. Weather and boat speed can reduce the max flow by a lot so engines like Lehmans may not pump much at all. The concept is popular, but not always practical other than " more help" but not a primary dewatering pump.

Yup. On a big, fast boat with big engines that move a ton of water, it makes sense. But even my gas big blocks are only rated to move 30 gpm through the raw water system (and that's at high RPM), so if I really wanted an engine driven emergency pump, something belt driven would be far more effective.

 

[psneeld]

Plus the engine intake method... you have a lot going on, and now you have to manage the flow to the engines.

With the boat rolling and water getting low.......It may cause overheating ....you have to decide whether you need to get to the seacock or shut down the engine.

 

[rgano]

My engine's raw water pump with put out 2140 GPH at 3800 RPM, but am I going to be down in the tiny narrow space trying to make sense on the situation with that racket going on while trying to make sure I don't burn out the raw water pump accidentally. No way. Bad idea. Better to have a separate belt-driven pump with a clutch and or a prop shaft pump which will run while you are running for help or to a beaching.