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Old 10-26-2015, 10:38 PM   #1
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Jet Thrusters - Does anyone have this system?

Saw this thruster system. Wonder if anyone has one and how well does it work?
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Old 10-27-2015, 05:43 AM   #2
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Don't know any one who has them, but they certainly look impressive and easy to fit.
Would hate to break a line, could quickly flood your boat ?

Cheers Chris D Liberty
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Old 10-27-2015, 10:17 AM   #3
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Your boat has hudraulic jet bow thrusters. Made by omnie thrust. Our thruster is the smallest they the are mostly on larger ships ferry. They are so so. The advantage is being hydraulic which can run for hours as long as the engine runs. The disadvantage I'd it takes to long to switch to the other side. The thruster has a hydraulic motor rated 2500 psi and the hose are 3000 psi, and the thruster is made of SS 3/8". The thruster is powered by the gen set which does not have the hp for what thrust is rated for.

The hydraulic has quick change hose coupling to power the get home. I changed the hydraulic pump to variable psi with a cable up to the pilot house so the thrust is 0 to 1800 psi. If the thrust I would change to standard propeller type as the pump is also reversible. But for now the work for our fair weather boating.
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Old 10-27-2015, 10:46 AM   #4
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Re: Post #3...What?
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Old 10-27-2015, 11:06 AM   #5
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Old 10-27-2015, 11:39 AM   #6
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The concept here is intriguing.

Take a high pressure, high volume pump and direct it's output where you need it.

This is opposed to the traditional thruster methodology of taking a low pressure high volume pump and installing it directly perpendicular to the hull.

The challenges are significant but not impossible to overcome. For example I did not notice sea cocks on these huge below the waterline through hulls. That seems like a risk to me, but the design could be modified to utilize a proper sea cock.

What I am wondering is if this concept of a pump and high pressure seawater stream could be used to provide roll dampening. If that worked out then it would provide an alternative to traditional fin stabilizers.
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Old 10-27-2015, 11:45 AM   #7
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The sizing tool on the site indicated they don't have a system large enough for a 50' cat. Seems if your boat is large enough to need thruster(s), they can't help.
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Old 10-27-2015, 11:56 AM   #8
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It will not be as efficient as a prop thruster. Not that efficiency is a big deal for a thruster, it is that the gennie and main engine at idle simply don't have a lot of available hp. So factor in hyd system losses, big centrifugal water pump losses, piping losses, and the basic inefficiency of jet propulsion and your available 20-odd hp ends up being a few hp worth of thrust.

In other words, weak thruster.

Still a neat concept, and there may be apps were it could work very well.
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Old 10-27-2015, 12:20 PM   #9
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As I've said before, alcohol and the interweb don't mix well.
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Old 10-27-2015, 12:23 PM   #10
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What I am wondering is if this concept of a pump and high pressure seawater stream could be used to provide roll dampening. If that worked out then it would provide an alternative to traditional fin stabilizers.
Between reaction times and maximum forces generated I doubt it can be made to work engineering and/or cost wise.
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Old 10-27-2015, 02:04 PM   #11
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Between reaction times and maximum forces generated I doubt it can be made to work engineering and/or cost wise.
I suspect you are correct. Someone had to have thought of that before.
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Old 10-27-2015, 02:46 PM   #12
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I like this idea. Would want to know much more about the pump before I plunked any money down.

I always thought that an azimuthing eductor nozzle under the hull would be a interesting design concept. Two diametrically opposed educators mounted athwartships with a y-valve would even be simpler.

Good eductors move 4x the amount of water supplied as the motive force.
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Old 10-27-2015, 03:00 PM   #13
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Gonna scare the crap out of the dolphins that follow my boat.
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Old 10-27-2015, 03:03 PM   #14
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A related idea-

Forward- 2 pumps, outlets mounted directly to the hull (port and stbd sides), fed by a common thru hull. Pumps are electrically activated as needed to provide thrust action.

Aft- as above, only the pump feed is directly below the pump itself.

A bit more complex, but there is not pressurised water flowing thru the vessel from a common centrally mounted pump.
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Old 10-27-2015, 03:40 PM   #15
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A related idea-

Forward- 2 pumps, outlets mounted directly to the hull (port and stbd sides), fed by a common thru hull. Pumps are electrically activated as needed to provide thrust action.

Aft- as above, only the pump feed is directly below the pump itself.

A bit more complex, but there is not pressurised water flowing thru the vessel from a common centrally mounted pump.
I like that Pete!

Then you'd need two solenoid valves, one per direction. The joystick turns on the pump and opens the proper solenoid valve

So, how many HP is a thruster for say a 45-50' boat?
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Old 10-27-2015, 04:28 PM   #16
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Per Lewmar., somewhere in the 8-10hp range.
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Old 10-27-2015, 04:43 PM   #17
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Maybe you could point them down to add a bit of lift and another 10 knots.
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Old 10-27-2015, 04:48 PM   #18
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How about a reversible pump (if there is such a thing) that would suck water thru one port and shoot it out the other. Then reverse the pump and move in the other direction. This would eliminate a thru hull and solenoids. I'm no engineer so don't laugh at me!
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Old 10-27-2015, 05:13 PM   #19
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To get the pressure needed, it really needs to be a centrifugal pump, and those are not reversible. Other pumps out there are reversible, but not as simple, compact and elegant as a centrifugal. Also, you want the suction line to be much bigger than the jet nozzle, so that screws up a reversible system.

I think they did it the best way: One suction, one pump, select thrust direction with remote operated valves.
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Old 10-27-2015, 05:26 PM   #20
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Maybe you could point them down to add a bit of lift and another 10 knots.
Or connect a hose for a super anchor & chain washdown system
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