Powering Hydraulics

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MikeM

MikeM

Senior Member
Joined
Jul 6, 2012
Messages
281
Location
USA
Vessel Name
Tuscan Sun
Vessel Make
Krogen 42
We are looking at a boat that has hydraulic stabilizers and bow thruster. They run off the generator. I'm not sure I like that arrangement since we would have to run the generator to use either. Are there any benefits to this set-up? Any idea of cost to reroute to the single main engine?

Thanks.
 
most boaters underutilized their gensets... that setup sounds OK to me,,
 
psneeld said:
most boaters underutilized their gensets... that setup sounds OK to me,,
Click to expand...


We expect to travel from Virginia to Florida each winter, so we will put some miles on the boat. This set-up doesn't sound very fuel efficient to me. If I get between 3 and 4 NMPG without the generator, why would I want to increase my fuel consumption by 50 to 75 percent? Is there any other benefit besides getting more time on the genset?

I guess I should have been clearer in my original post. I really think I want to move the hydraulic pump to the main engine. Any idea of the cost to do that?
 
The only thing I can think of is the generator runs at a fixed RPM giving a predetermined and constant hydraulic pressure to the stabilizers. In heavy seas, you may have to slow your mains down which is just when your stabilizers are working hardest. I don't have them so this is pure speculation.
 
dimer2 said:
The only thing I can think of is the generator runs at a fixed RPM giving a predetermined and constant hydraulic pressure to the stabilizers. In heavy seas, you may have to slow your mains down which is just when your stabilizers are working hardest. I don't have them so this is pure speculation.
Click to expand...


Actually, that is what I been told is the advantage.
 
The only negative I can think of for running off the main engine is that when you want to use the thrusters, you'll probably be at idle and may have not have enough pressure without bumping up the main a bit? Not sure.
 
A varable displacement piston pump would solve that. Mate it to an electric clutch and short shaft forward of the main pulley. Or look for a pto option on the transmission to drive the pump. If you plumb it right you could have both available as an either or option. Good luck.
 
Are you certain the boat doesn't have hydraulic steering? It doesn't seem to make a lot of sense to install hydraulics for a thruster and stabilizer. My suspicion is the engine at idle doesn't produce enough RPM's to run the hydraulics with the thruster on so they were off loaded to the generator. Perhaps, you should consider another boat or at least have the surveyor look at it.
 
MikeM said:
We are looking at a boat that has hydraulic stabilizers and bow thruster. They run off the generator. I'm not sure I like that arrangement since we would have to run the generator to use either. Are there any benefits to this set-up? Any idea of cost to reroute to the single main engine?

Thanks.
Click to expand...
Not such a good idea since it means you are running the genset to provide the minor fluid flow that the stabilizers need. Delfin was kind of set up that way when I bought her, although the only setup was a pump on the genset and no hydraulics. I added a pump via a drive shaft off the flywheel on the CAT, which generates more than enough flow when cruising for the stabilizers plus hydraulic washdown, de-watering pump, etc. When I want full flow for the thrusters I fire up the genset.

You wouldn't like having to run the genset all the time and most main engines can easily accommodate a pump for the stabilizers.
 
MikeM said:
We expect to travel from Virginia to Florida each winter, so we will put some miles on the boat. This set-up doesn't sound very fuel efficient to me. If I get between 3 and 4 NMPG without the generator, why would I want to increase my fuel consumption by 50 to 75 percent? Is there any other benefit besides getting more time on the genset?

I guess I should have been clearer in my original post. I really think I want to move the hydraulic pump to the main engine. Any idea of the cost to do that?
Click to expand...
A lot.

However, it would be far better for it to be on the main if that is the only source of fluid you want to have, rather than both the main and the genset, which costs even more. You can use the thrusters if the main engine is the only fluid source, but they take a lot of flow so you would have to go to throttle override, rev the engine up, engage the thrusters, go to neutral, off with the throttle override and engage the gear. Certainly can be done, but it gets a bit tiresome. At idle, you will not likely have enough flow for thrusters. The pump I am using off the CAT is a honker so that I can get about 3/4 flow for bow thrusters only, which is why I start the genset if I want to use both bow and stern or need max power on the bow only.

ABT can design the system for you and tell you what it will cost. They are great engineers.
 
My boat has hydraulics running windlass, stabilisers, AP and Davits from two pumps running off the main.

I'm happy enough with that setup, but if I had the cash, I'd run the windlass circuit off the generator, because when weighing or setting anchor in any real breeze, I have to throttle down to adjust boat position, then throttle back up to continue with the anchor etc etc.

It's a fun juggle in tight anchorages.

FWIW, I think you might have a similar hassle needing thruster revs from the main.
 
My windlass, and BT are run off of a belt driven pump from the main engine. Idle only is needed for either. Its all in the pump sizing and associated piping. I agree completely with Delfin on ABT, tell them your requirements and what you want to do and they can put it together for you.
 
Couple points on hydraulics:
Looked at converting my bow thruster to hydraulics off the main. Used a commercial hydraulic / waterman's mechanical shop as opposed to the bow thruster manufacturer. Was going to run a large pump with an electronic clutch and a proportioning valve to control flow. System was designed to provide full power from the thruster at idle or above. By the time I added up all the parts to make the system and put the hydraulic motor on the thruster, I was over $7K. For $1.8K I converted the bow thruster to 24 volts including a dedicated battery bank and charger.

Was talking to my boat broker who is a Krogen sales rep. He said that Krogen has been doing hydraulics off the gen set for a while. He also said that they caution their customers to turn off some of the ac circuits when anticipating bow thruster use. Apparently there have been a few incidents where the gensets were under a substantial ac load while docking and hitting the bow thruster stalled the gen set. :eek:

If I was going to set up the hydraulics off the main engine, I would definitely have an electronic clutch on the pump. Saves fuel and wear and tear on the hydraulic system when you are not using the stabilizers or the bow thruster.

Ted
 
Donsan said:
Are you certain the boat doesn't have hydraulic steering? It doesn't seem to make a lot of sense to install hydraulics for a thruster and stabilizer. My suspicion is the engine at idle doesn't produce enough RPM's to run the hydraulics with the thruster on so they were off loaded to the generator. Perhaps, you should consider another boat or at least have the surveyor look at it.
Click to expand...


I'm not sure about the steering. Looked like hydraulic, but broker says hynautic. I'll confirm if/when we do survey.
 
Delfin said:
A lot.



However, it would be far better for it to be on the main if that is the only source of fluid you want to have, rather than both the main and the genset, which costs even more. You can use the thrusters if the main engine is the only fluid source, but they take a lot of flow so you would have to go to throttle override, rev the engine up, engage the thrusters, go to neutral, off with the throttle override and engage the gear. Certainly can be done, but it gets a bit tiresome. At idle, you will not likely have enough flow for thrusters. The pump I am using off the CAT is a honker so that I can get about 3/4 flow for bow thrusters only, which is why I start the genset if I want to use both bow and stern or need max power on the bow only.



ABT can design the system for you and tell you what it will cost. They are great engineers.
Click to expand...


My broker is trying to get some cost info from American Diesel in Virginia. Who/where is ABT?
 
Most of the newer Nordhavns less than 60 feet have stabilizer hydraulics run off main and electric thrusters and windlass. Our DeFever is set up this way with the Vickers hydraulic pump run off a PTO on the back of the transmission and an electric thruster and windlass.

In the last decade or so thruster technology has developed to the point that the old bugaboo of timing out is not much of an issue. My thruster will run at least 2 minutes, tested it and finally just gave up as it kept cranking away.

There is no right or wrong way, just different to do this setup. But definitely, as pointed out, you can easily come up with a setup where running your genset is not necessary to gain hydraulic pressure. But, in your case is it worth it?
 
My set up

My stabilizers run off the port engine. One of the things not mentioned is that you should always run your stabilizers underway. My Niads relax and need to run to be in the proper position to reduce drag. I don't have a bow thruster on this boat but I have operated a hydraulic thruster that was engine run. This one required that the engine be running at about 1400 rpms to be effective, so docking required throttle, shifter, and thruster manipulation. Somewhat of a handful. A lot of boats were built with the intention of running the generator full time while underway. Most commercial boats operate this way. I run my boat with the 8 kw generator running most of the time. Air conditioning, heat and galley are all electric. Generator under light load requires little fuel.
 
I think the confusion is that you have two different situations, with two different answers.

Stabilizers don't require a lot of hydraulic power, so operating off a main engine driven pump works fine. It could be either fixed displacement or variable displacement, with the later being more elegant and more expensive. Powering off the main engine removes the need to run the generator all the time, which I think is what you are hoping to accomplish.

The other situation is docking when you want to use your thrusters. Thrusters use significantly more power than stabilizers, and powering them off the main engine is likely not practical. The problem is that when docking your main is at idle, so to get enough flow for the thruster you need a really big pump. Engines and transmissions have limits on how big a pump you can put on them, and that will typically not be enough for good thruster performance. The common solution is to put the pump on an engine that's running at 1800 RPM or more instead of 600 RPM, so that means the generator or a wing engine if you have one. The ideal setup would have the biggest pump that will fit on the main engine to run the stabilizers underway, and to provide partial power to the thrusters while at idle. Then a second pump on the generator (I'll assume no wing engine, but it could go there as well) to provide the additional power needed for full thruster performance.

Now all this really depends on the specifics of your boat. How big is your main engine, how big a pump can it take, what's it's idle RPM, how much power do your thrusters require, and how much more is needed than your main can provide?
 
My engine-driven hydraulic pump runs continuously without a clutch and has done so for 19 years.
 
twistedtree said:
I think the confusion is that you have two different situations, with two different answers.

Stabilizers don't require a lot of hydraulic power, so operating off a main engine driven pump works fine. It could be either fixed displacement or variable displacement, with the later being more elegant and more expensive. Powering off the main engine removes the need to run the generator all the time, which I think is what you are hoping to accomplish.

The other situation is docking when you want to use your thrusters. Thrusters use significantly more power than stabilizers, and powering them off the main engine is likely not practical. The problem is that when docking your main is at idle, so to get enough flow for the thruster you need a really big pump. Engines and transmissions have limits on how big a pump you can put on them, and that will typically not be enough for good thruster performance. The common solution is to put the pump on an engine that's running at 1800 RPM or more instead of 600 RPM, so that means the generator or a wing engine if you have one. The ideal setup would have the biggest pump that will fit on the main engine to run the stabilizers underway, and to provide partial power to the thrusters while at idle. Then a second pump on the generator (I'll assume no wing engine, but it could go there as well) to provide the additional power needed for full thruster performance.

Now all this really depends on the specifics of your boat. How big is your main engine, how big a pump can it take, what's it's idle RPM, how much power do your thrusters require, and how much more is needed than your main can provide?
Click to expand...


Thanks TT...that explanation helps a lot. I am going to look into the cost of that set-up.
 
Thanks to all for the info. It's amazing how much you can learn on this forum...and how quickly.
 
One more question...which I think I already now the answer to. Do I need to have the stabilizers ON or CENTERED continuously when underway? I think the answer is YES...and both conditions require the hydraulic pump and generator (on this boat) to be running. What happens if the stabilizers are turned off underway?
 
First of all what brand/type/model of stabilizers are these? Various makes and designs work different ways. Lots of wild jumping to conclusions here with scant information. For instance if they are standard Naiads, then yes, you should have them on all the time, centering is for docking. Naiad is very helpful and could advise on the conversion. In theory (again lacking good info) having the thruster on the generator and the stabilizers on the genset makes the most sense.
 
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Greetings,
Mr. MM. To the best of MY knowledge, stab's should be on while underway (if centered, I don't think they'd be doing much if anything) and centered while slow maneuvering (if on while slow maneuvering it really screws up where you want the boat to go-don't ask me how I know this). Our Naiads are powered by a two belt pump run off the front of our port Lehman-no clutch).
Our Naiads have pins to lock the stab's in a centered position when off. I hate to think what would happen if we engaged the stab's with the pins in place so I usually leave the pins out.
Rats, Mr. C beat me by 3 minutes...
 
MikeM said:
We expect to travel from Virginia to Florida each winter, so we will put some miles on the boat. This set-up doesn't sound very fuel efficient to me. If I get between 3 and 4 NMPG without the generator, why would I want to increase my fuel consumption by 50 to 75 percent? Is there any other benefit besides getting more time on the genset?

I guess I should have been clearer in my original post. I really think I want to move the hydraulic pump to the main engine. Any idea of the cost to do that?
Click to expand...

Your Genset in most cases would not be burning 50-75% what your mains are.

The only change I would consider making is to run the stabilizers off the main/s. And I would put a PTO on both engines if you have twins. Or you could perhaps run the stabilizers off a DC hydraulic power pack if you can find one with the correct flow and rated for continuous duty. But if that gives you sticker shock then don't worry about it. You will how ever have to lighten or eliminate entirely the AC load on your Genset when you go to use your thruster.

If you have any questions on switching to engine driven PTOs, call Justin at TRAC +1 (954) 253-8047 or Burt at ABS Hydraulics (954) 593-3727
 
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MikeM said:
What happens if the stabilizers are turned off underway?
Click to expand...

They can flop around and cause drag and steering issues. If you loose the Genset or hydraulic power you would need to manually lock/pin them in the center position.
 
Capt.Bill11 said:
Your Genset in most cases would not be burning 50-75% what your mains are.



The only change I would consider making is to run the stabilizers off the main/s. And I would put a PTO on both engines if you have twins. Or you could perhaps run the stabilizers off a DC hydraulic power pack if you can find one with the correct flow and rated for continuous duty. But if that gives you sticker shock then don't worry about it. You will how ever have to lighten or eliminate entirely the A/C load on your Genset when you go to use your thruster.



If you have any questions on switching to engine driven PTOs, call Justin at TRAC +1 (954) 253-8047 or Burt at ABS Hydraulics (954) 593-3727
Click to expand...


Thanks for the info CAPT. I'll give them a call.
 
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