2 inch dredge ..no suction

[jwwynacht]

I have a 2 inch dredge / high banker combo I put together. it is a keene a 52 sluice with a jobe 2 inch highbanker / dredge hopper. The sluice has a jobe stand it sits on as well. I'm using a jobe suction nozzle that has a 1.25 inch pressure hose and a 2 inch suction hose. I have 20 ft of 1.25" pressure hose. 20 ft of 2" suction hose and about 6 ft of 2 inch for the pickup hose. I have a jobe footvalve and made sure I primed the pump so there was no air in the foot valve. I'm running a 3 horse predator engine with a pump that's supposed to be 325 gallons per minute. it has a 2 inch cam lock and 2 reducers the first is 2 to 1.5 and then another one that's 1 to 1.25. when I first cranked the pump on it was pumping but just a slow trickle was coming out of the sluice. it was slightly leaking a small amount of water in between the pump and the engine..the pressure hose ended up coming loose and popped off the nozzle.. it had good pressure..it blew water about 15 feet and almost shot out of my hand. I turned the pump off and reattached it but still couldn't get it to pump enough to vacuum. I moved the sluice and pump and repositioned everything so the pump was upriver pumping downward to the nozzle and then the sluice sat further down river..still nothing..after a few hours of messing with it, it quit picking up water and pumping all together..am I using too much hose? or maybe a bad seal? and possibly bad plastic reducers? I'm not sure what brand pump but ive seen videos of the same one running a 4 inch dredge and he claimed it was only half throttle. I cant find the exact pump I have but here is a smaller version..it says its 200 gallon per minute 2 inch inlet with 1 and 1/2 inch discharge..mine was a 2 inch inlet with 2 inch discharge that was supposed to be 325 gallon per minute. It was built by the same guy. .backwoodz prospecting..

Gold Dredge Motor & Pump High pressure 200GPM FREE SHIPPING IN THE LOWER 48

 

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[okbasspro]

Sounds like you have a bad seal. Get you a name brand pump and save some headaches I've been there and done that.

 

[Vance in AK]

I know that guys pumps have a pretty good reputation on other sites. First thing, reducers should be at the nozzle, not the pump. Running the larger hose as far as the nozzle will give you better volume & pressure because there is less friction loss. Did you check for restrictions in the nozzle it self?
Foot valve didn't get plugged with leaves etc did it?

 

[mike(swWash)]

Check all the fittings and gaskets on the suction hose to the pump. Even a pinhole sized leak will cause cavitation in the pump and no flow or pressure coming out. This is why I use clear suction hose so I can see these things and also why I carry a roll of gorilla tape

 

[jwwynacht]

I did find a rock jammed in the nozzle today. I'm not sure if that was there before or if it was new but hopefully was the problem.

 

[Vance in AK]

Be sure and check with a flashlight in the pressure intake side of the nozzle. Take something flexible (like a piece of CLEAN gas line) amd run it around thay bend and make sure nothing is lodged in there. Or is that where the rock was? And if you havent already check the entire suction hose including the pipe that enters the highbanker box for obstructions.
If removing the rock you found doeznt fix it start at the nozxle by pulling the pressure hose off. If you dont have goid pressure/volume there work your way back fitting by fitting toward until you find your restriction.
When you fire the pump up that water from the pump should be coming out the sluice or intake end of the suction nozzle ( with the nozzle out of the water).

Forgive spelling errors. My thumb is too big for the phone

 

[brianc053]

I did find a rock jammed in the nozzle today. I'm not sure if that was there before or if it was new but hopefully was the problem.

Quick story: last year I took my 3" dredge down to Virginia, spent 30 minutes getting it all set up, got the pump running - no suction. I checked everything, and eventually took the nozzle off the hoses, shook it and an acorn fell out. Problem solved, right? Reattached the nozzle, got everything set up again (another 30 minutes) and...no suction. Took the nozzle back off the hoses and found two MORE acorns jammed in the jet.
Apparently at some point a squirrel got into my garage and thought the nozzle was a good place to store his/her acorns for the winter.
Lost 60+ minutes worth of dredging time, but learned about one more thing to check before I start up the pump!
Sorry to hijack the thread.
- Brian

 

[seekerGH]

Sounds like it is not priming.

it has a 2 inch cam lock and 2 reducers the first is 2 to 1.5 and then another one that's 1 to 1.25.

this is a problem. All of the energy is being wasted at the pump. By theory, reducing it at the pump like this can cause cavitation simply with the friction loss in the reduction. As another poster stated, it should be reduced at the end, not the beginning.

As an example....

 

[jwwynacht]

how do you reduce it where it meets the suction nozzle?

 

[jwwynacht]

and so far the pump has been great I'm happy with it

 

[mike(swWash)]

Is it the one in the link?
If so, have you checked the output pressure with a gauge? Measured the output volume yourself?
I ask because I have been looking at these for a while but I never trust sellers info....only true users info and I'd like to have one as a backup pump or as my primary if it works as advertised.

 

[akflyer]

This would be useful info for the rest of us as well. I have been eye balling them and very curious if they hold up the way they claim. If so, I will have a couple of them set up for next season.

 

[Vance in AK]

how do you reduce it where it meets the suction nozzle?

Run 2" layflat or other pressure hose from the pump to the nozzle & then reduce it to the 1.25" same as you did on the other end.

 

[brianc053]

Run 2" layflat or other pressure hose from the pump to the nozzle & then reduce it to the 1.25" same as you did on the other end.

^This. My setup has 2" lay flat coming out of the pump and running close to the nozzle, but then I use 8' of 2" rigid between the lay flat and the nozzle because a) the rigid is actually easier to maneuver near the nozzle than the lay flat despite the "rigid" name, b) the section near the nozzle will get beat up and lay flat is easier to puncture than rigid, and c) someone smarter than me told me I should do this, so I did.
See picture (that's my son, who loves running the nozzle).
If you wanted to drop the 2" down to 1.25" you could do it at the junction between the 2" lay flat and the rigid part going into the nozzle.
- Brian

 

[Vance in AK]

Perfect Brian

 

[seekerGH]

Sorry, have not been back to this thread.

OP...you stated this...

I'm running a 3 horse predator engine with a pump that's supposed to be 325 gallons per minute. it has a 2 inch cam lock

But the link you provide states 200gpm and a 1.5 inch outlet. Which is it please. If it is the 3.5hp with 1.5 outlet, the chart below will show you the performance. I see about 140GPM at zero pressure...

Every pump should have a pump curve with it. The curve shown in post #8 is good enough for a pump with a 2" outlet, and shows the difference in flowrate for the same pressure. (is also for rigid PVC not flex).

​

Looking at 0 head numbers, it takes an 8HP Honda motor to deliver that GPM. As the chart notes, if you want PSI, divide head by 2.31. So, zero pressure in the outflow, ie freeflow gets you that GPM.

The 5.5HP only can deliver 175GPM at zero head pressure.

Horsepower to maintain the flowrate under pressure is another factor, as is the length of the pipe. I am curious how a 3HP motor with a 2" outlet gets you 325GPM?

 

[akflyer]

Sorry, have not been back to this thread.

OP...you stated this...



But the link you provide states 200gpm and a 1.5 inch outlet. Which is it please. If it is the 3.5hp with 1.5 outlet, the chart below will show you the performance. I see about 140GPM at zero pressure...

Every pump should have a pump curve with it. The curve shown in post #8 is good enough for a pump with a 2" outlet, and shows the difference in flowrate for the same pressure. (is also for rigid PVC not flex).


View attachment 1494612 View attachment 1494613

View attachment 1494614​

Looking at 0 head numbers, it takes an 8HP Honda motor to deliver that GPM. As the chart notes, if you want PSI, divide head by 2.31. So, zero pressure in the outflow, ie freeflow gets you that GPM.

The 5.5HP only can deliver 175GPM at zero head pressure.

Horsepower to maintain the flowrate under pressure is another factor, as is the length of the pipe. I am curious how a 3HP motor with a 2" outlet gets you 325GPM?

Big difference between a pressure pump and a trash pump... putting a valve or restriction on the outlet of the pump doesn't cause cavitation, restricting the inlet side does though. At the end of the day, if your using the pump on a suction dredge, your reducing it down to around 3/4" correct? the only way to get more flow through that hole is with pressure, not volume.

 

[seekerGH]

At the end of the day, if your using the pump on a suction dredge, your reducing it down to around 3/4" correct? the only way to get more flow through that hole is with pressure, not volume.

Exactly. The OP original specs are looking at volume, and the diagram in post #8 is a pressure pump diagram.

For the dredge, it has a pressure pump, so you need pressure and volume to rune the dredge. That is why I dont think that a 3.5 HP motor can deliver the specs as stated.

On a pressure pump, necking it down at the source will cause cavitation, when the fluid moves too fast through the restriction to the unrestricted pipe section. At the end on the nozzle, you have the loss through the pipe with the diameter friction and pipe length.