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Old 04-04-2012, 05:28   #1
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Hydraulic Bow Thruster

My new (old) boat has a hydraulic bow thruster, I guess from 1981 its been disconnected and not in use, no pump, no controls, anyone know anything about these, have any opinions? I dont know the make but would like to make it work again.
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Old 04-04-2012, 06:37   #2
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Re: Hydraulic Bow Thruster

Name, rank and serial number.
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Old 04-04-2012, 06:39   #3
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Re: Hydraulic Bow Thruster

I have used hydraulic bow thrusters a few times
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Old 04-04-2012, 07:03   #4
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Re: Hydraulic Bow Thruster

You need a pump/tank/solenoid combo mounted in the bow. I beleive this might be easier than engine hyd. powered. If mounted in the bow you would only need to run 2 sets of wires back, 2 massive power cables to a battery bank, a 5 pack maybe for solonoid trigger wires, and a on/off switch. The solenoid wiring can be small low amp stuff, its not doing any work. But the power feed cable is gonna be big and costly, not many ways around it. I bet for $3000-$5000 you could have it working. 60ft is big though that pump might cost $5k alone, and $1500 for wire if you source it well. Do it yourself and those would be the bulk of your cost. The up side is you could run a huge windlass off those same power cables.
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Old 04-04-2012, 07:10   #5
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Re: Hydraulic Bow Thruster

Ok, I'll give in too....
Most often hydraulic thrusters are run as a PTO pump off of a generator or main engine. The generator is the preferred source imho.

Other sources can include an electric power pack in the bow.

Either way there are a lot of ways to go with this, on/off solenoid valves, proportional valves, etc........

You can build yourself a kit, or just buy a kit and start anew.
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Old 04-04-2012, 08:04   #6
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Re: Hydraulic Bow Thruster

Hydraulic bow thrusters are fantastic. As are hydraulic winches and windlasses. But one bow thruster unit which may have been out of commission for decades, and with no pump or controls, is a very small start to a working hydraulic system on board, in fact, it's probably equal to zero, depending on what is required to get the old thruster working again. You might very well be better off starting from scratch, and if starting from scratch, it will be vastly cheaper just to put in an electric bow thruster.

Probably the best way to start would be to take it out and have it looked at. It will likely need a complete overhaul and might be unrepairable. Get an estimate on installation of a new electric bowthruster and weigh your options.

If I had unlimited money (a counterfactual hypothetical question), I would install a hydraulic pump on my genset and replace my electric windlass and my bow thruster with hydraulic. I reckon it would cost a fortune, however. Electric works pretty well, especially if you have 24 volts on board as I do.
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Old 04-04-2012, 08:51   #7
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Thanks guys, all good info. I currently have an electric windlass in the same locker with one AGM battery, there is plenty of room for more batteries. how many do you think it would take to move a fifty thousand pound boat around? I agree hydraulic would be nice for both thruster and windless but cost may be prohibitive. I was hoping I could just use the unit that was installed run new lines and get a pump, controller and reservoir and go for it but I dont know anything about the maint issues with the thruster part. I assume if you take that part out you have to haul the boat to switch it out? any way to get it out from the inside with plugs in the tunnel? Why run the hydraulics off the generator? wouldn't you always have the main engine running while trying to dock?
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Old 04-04-2012, 09:02   #8
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Re: Hydraulic Bow Thruster

I was under the impression that only the smallest of bow thrusters were straight electric. And most were hydro from electric pump or from engine/genset pump. I agree that the hydro thrust motor is probably the smallest part of the system, and probably wouldnt cost to much to have it rebuilt/seals replaced. Thats if the lines were plugged and no water got in. It could be seized. Did you spin it when boat was hauled?
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Old 04-04-2012, 09:07   #9
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yes it was free, and turned. I'll go out this friday and see if I can pull numbers off it. Any suppliers out there for this stuff anyone used?
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Old 04-04-2012, 09:11   #10
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Re: Hydraulic Bow Thruster

Its nice to have different RPM's at your prop and thruster. If you want to be in gear slowly in forward your bow might not respond with low idle, so you would have to put it in neutral to speed up thruster speed. Not very practical. Its the same with tow truck PTO pumps and other multi motor PTO applications.
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Old 04-04-2012, 11:22   #11
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Now that makes sense, I guess to avoid that you would have to get a pump that works at capacity at idle rpm, or like mentioned before run it off the genset, it has a 16 kw phaser wonder if that would do it. although the electric is starting to sound like a better option, could always use more batteries I guess!
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Old 04-04-2012, 12:03   #12
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Re: Hydraulic Bow Thruster

My boat weighs nearly 50,000 pounds and my Sleipner Sidepower 10HP thruster moves it around quite well. Yes, it is straight electric with a rather large electric motor with a vertical shaft mounted to the top of the drive leg.

It consumes over 10kW of power at peak, however, so requires serious batteries and wiring. As the boat was designed, it had a separate bank of 220aH * 24 V for the thruster and windlass (since integrated into the house bank). With 24v, the cable size is reasonable.

If your existing thruster is free and dry and can be rebuilt, then you might just price the installation of a pump on your genset. If it's not 10x the cost of fitting an electric thruster, it might be worth it -- when (not if) your electric windlass fails, then you can replace it with a hydraulic for very little money since you already have the pump. Might be worth it.
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Old 04-04-2012, 13:04   #13
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problem is my generator is about 50 feet from the bow thruster, thats a bunch of hydraulic line and I wonder what that distance does to hydraulic pressure loss due to friction?
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Old 04-04-2012, 13:13   #14
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Re: Hydraulic Bow Thruster

I think you already said you have DC windlass (12volt) ? If so all you need is one more battery to run a 10hp 24VDC thruster. Batteries are charged from your regular 12volt souce but with a series parallel switch installed, output can be 12VDC to the windlass and 24VDC to the thruster. This is by far the cheapest option.

You can pay Vetus about $1200.00 for a series/parallel switch or buy one from a farm supply/tractor repair outfit for about $150.00
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Old 04-04-2012, 13:35   #15
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Re: Hydraulic Bow Thruster

No friction loss with the fluid, not that you would notice. Or lag time, hyd. fluid displacement is instant. Look at all the long runs on the average excavator/tractor, a auto flatbed with a 24' bed has 2 -48' line runs. Still instant. Hyd lines are probably cheaper than huge tinned electric cables, but the pump and mount for gen wont be cheap.
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