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Old 10-17-2014, 06:12 PM   #1
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Powering Hydraulics

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.
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Old 10-17-2014, 06:21 PM   #2
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most boaters underutilized their gensets... that setup sounds OK to me,,
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Old 10-17-2014, 06:33 PM   #3
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most boaters underutilized their gensets... that setup sounds OK to me,,

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?
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Old 10-17-2014, 06:42 PM   #4
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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.
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Old 10-17-2014, 06:43 PM   #5
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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.

Actually, that is what I been told is the advantage.
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Old 10-17-2014, 06:59 PM   #6
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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.
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Old 10-17-2014, 07:16 PM   #7
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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.
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Old 10-17-2014, 08:58 PM   #8
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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.
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Old 10-17-2014, 09:04 PM   #9
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Originally Posted by MikeM View Post
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.
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.
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Old 10-17-2014, 09:06 PM   #10
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PTO or Belt driven?
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Old 10-17-2014, 09:10 PM   #11
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Originally Posted by MikeM View Post
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?
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.
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Old 10-17-2014, 09:41 PM   #12
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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.
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Old 10-17-2014, 10:02 PM   #13
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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.
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Old 10-17-2014, 10:10 PM   #14
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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.

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.

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Old 10-17-2014, 10:19 PM   #15
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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.

I'm not sure about the steering. Looked like hydraulic, but broker says hynautic. I'll confirm if/when we do survey.
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Old 10-17-2014, 10:20 PM   #16
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PTO or Belt driven?

Sorry...don't know.
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Old 10-17-2014, 10:27 PM   #17
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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 broker is trying to get some cost info from American Diesel in Virginia. Who/where is ABT?
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Old 10-17-2014, 10:42 PM   #18
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My broker is trying to get some cost info from American Diesel in Virginia. Who/where is ABT?
ABT-TRAC
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Old 10-17-2014, 11:15 PM   #19
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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?
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Old 10-17-2014, 11:17 PM   #20
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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.
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