Hey All, took my new to me 8” submersible out today and found it did not have nearly as much suction as I was expecting. Had a hard time picking up 4-5” rocks.. Guy I got it from claimed he ran it 20+ years ago with a keene 4x3 pump on a gx390, 3” flat hose and 15’ of suction hose.
Looking closer at the nozzle it goes from 3” down to 1.25” and possibly has a washer/reducer welded in the bend on the jet. I’m not a rocket surgeon but this seems to be too small. my question is should I jump up to 1.5” or 1.75”? And if there is supposed to be a washer/reducer what size should it be?
I tried running it with 2 pumps and the suction got worse like they where fighting each other. I cut the 3” hose in the picture down to 8” and was running 15’ of 1.5” GX160 Proline 300 pump.
My Gx160 with proline 300 only runs my 6inch reduced down to 5inch nozzle - semi sub dredge..it has 2inch hose pipe down to a reduction of 27mm
My gx390 with a proline 400 or 500 whatever their largest pump is would run that and be what you are looking for with 3inch hose all way to nozzle.. I don’t think it is necessarily the suction nozzle jet of inch and quarter that should be ok..esp if old boy ran it that way..
and also the middle bit won’t have a washer it will be where weld joined two sections.. some of my old nozzles have the same
Each pump requires a different size jet. You match the pump to the outlet of the jet. I’m running twin p350 30mm jet orifice on an 8”. You’re running a suction nozzle so you may get away with something similar with one pump on your set up. Seems the old owner might’ve had it right. Your set up is way under powered if I’m reading it right. You have to get the volume and psi up on water flow. I’m easy to contact if you want to ph.
Are you familiar with the fact one 18 inch pizza is more pizza than 2 12 inch pizzas ?
The 390 had more than double the hp. And that big pump had exponentially more flow than both those small ones at the same pressure.
It needs to be 3 inch all the way from the pump (pumps or where they join) so the water has plenty of momentum then gains velocity as it reaches the nozzle.
Get someone to fabricate you a nice steel Y joiner from both 2s to the 3 inch is the easiest other thing you can try. .
getting another nozzle put in the suction nozzle is probably the best solution to twin pumps on it.
Or put another one in it half along along like a power jet
Only way to truly measure the pizzas is by weight! Yes the old owner was running a bigger pump but he was also running 15’ of suction hose and using lay flat hose for pressure hose. After more reading and math I am on the look out for a used a 3x4/keene 350 and gx390. Or do ya’ll think a proline 500 on a gx270 would be enough? In the mean time I am going to build a fluid bed to hang off the back.
Worse part is now that I got a taste of the 8” it is going to be hard to go back to the 5!
I am going to cut that long 3” portion off and weld a 2” npt fitting on. Then try it with a Proline 500 pump 3x2. If the suction is still not great I will start playing with different reducer sizes. Does 1” cone shaped reducer sound like a good starting point for 8” with the P500?
475 GPM 35 to 45 PSI range, but it can sustain 60+ PSI.
Keep in mind it is a subsurface dredge. For context I run a 4” keene subsurface dredge with a honda ghx50 and p90 pump and a 5” with a Proline 200pump at 2/3 throttle. Much different power needs compared to a surface dredge.
Itl also depend on the depth you are dredging at. Submersibles are known for lack of suction at depth. I’m not sure on the mathematics but thought I’d mention. I run a 6 sub and love it, great dredges. Would love an 8”. Hope you sus it out
They dont lose any suction at depth. =) The entire dredge is under water. The deeper you go the whole dredge comes down with you. Just need to be able to push 7.5” rocks through 8 feet of tube.
I did manage to move a good amount of material running the one 5.5hp 300gpm pump. But I didn’t like that i had to throw any rocks bigger than 4-6”..
Yes I understand if you drop the box it should be fine. I believe it’s when the box doesn’t submerge as far as the nozzle people say they lose suction trying to pull gravels uphill the deeper ya go.
Im using a 6” submersible and run it off a 5hp honda and swimjoy. Plenty of suction. Sounds to me like you have enough grunt with your pump and motor, pretty likely it’s the jetting.. cant think.of much else, very simple units. That’s the beauty of them
Another thought I had, after I saw a comment you made under a pic that your bendy rod couldn’t get past where weld was, possibly a odd shaped stone has made it into the intake and past the pump and got lodged in causing lack of suction..I have had it with twigs before I got a finer mesh over my foot valve
There was a bunch of mud bug nests in the sluice box so you could be onto something! I am going to cut it up and redo it so I can swap out different reducers to get her dialed in.
Picked up a used Proline 500, cleaned up all the casting marks, got her semi polished, rebuilt a gx270 added a threaded crankshaft for the pump and this thing is a heavy BEAST! Ran the 8” great! Didn’t need to go full throttle. Now I am thinking about advancing the timing 3 degrees, bumping the compression a hair, gx390 carburetor and see if I can run it with 10’ of hose. And if it cant I will add a jetlog and second engine.
Place I am testing at has been hit hard over the years and not much gold left. Mostly just find flood gold in the sand bars and hard pack.
