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Old 03-08-2020, 02:04 PM   #1
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PTO on main, clutch or not?

I have a 57 Northern Marine trawler that has a pto on the main and one on the gensets. Both PTOs have a clutch. Im thinking about removing the clutch from the main. The clutch is taking up precious space and it has some potential reliability issues.

The boat uses hydraulics for stabilization, windlass, and thrusters, so its hard to imagine a time when I would not want hydraulics when the main is on. There is no issue with the hydraulics stalling the main and when I need more hydraulic hp I can engage the pto on the genset.

Is there any reason to keep the pto clutch in the main?

-mike
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Old 03-08-2020, 02:58 PM   #2
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seized pump could cause major damage if not disconnected.

Terry
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Old 03-08-2020, 03:37 PM   #3
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If you have a hydraulic failure, you could easily need to stop the pump. This could be caused by a pump failure itself, or a leak somewhere else that dumps the fluid. In either case, you need to stop pumping.


Now there are two things you can do.



1) disengage the PTO clutch which is quick and easy


2) Shut down, remove the pump, and install a cover plate over the PTO. Then secure the pump, and get back underway.


You have a windless and thrusters, so I'll bet the pump is big and heavy. Plus the hoses are big and stiff. Give it a try and see how easy it is to get the pump off, pulled out or the way, and secured. I did mine once to replace an o-ring, and it was not easy. Possible, yes, but not at all easy, and that was with a stable boat in a cool engine room.


If you go the removal route, definitely test it all out so you know the drill. Also, 9/10 times the PTO cover plate was tossed when the pump was installed, so you will have to go source a new cover plate. The best idea I've seen is to zip tie the plate to something right nearby so it's ready to go. Also check the mounting bolts. The bolts that hold the pump will be longer than what's needed for the cover. The longer bolts might work, but check to be sure. Also, many pumps bolt on with two bolts, but the cover plate needs four. Plus there might be an o-ring or other seal. So test the whole thing out and make sure you have all the necessary parts right on hand.


My first boat with hydraulics had a non-clutched PTO, but every boat since I have made sure that I have a clutch. But of course it can break too. Plus you need to test it periodically to be sure it works. Only you can decide what's best for you.
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Old 03-09-2020, 06:57 AM   #4
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If the PTO clutch is not reliable , replace it.
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Old 03-09-2020, 08:21 AM   #5
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I don’t know about reliability of the clutch, but I can tell you I wish I had them installed. Imagine a hydraulic leak on your stabilizers. Or imagine the hydraulic oil heat exchanger becomes plugged/fouled for some reason. Without an ability to disengage the pump, you could burn something up.

Just food for thought. Why are the clutches a reliability issue?
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Old 03-09-2020, 08:30 AM   #6
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I was considering changing my bow thruster to hydraulic. When talking to the local diesel engine shops, they usually setup hydraulic pumps on the commercial boats as continuous direct. From a reliability standpoint a lot of transmissions have a continuous running hydraulic pump powering the transmission clutch.

If I were considering switching from clutch to continuous duty, I might consider starting with a new pump. After the break in period, it would seem to be a more likely trouble free option. Might also want to buy a new oil cooler heat exchanger while you're at it.

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Old 03-09-2020, 11:04 AM   #7
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A fisherman I know had a hydraulic hose break and some fluid made it over the side. The fine was $2000. You need a way to quickly shut off the pump.
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Old 03-09-2020, 11:24 AM   #8
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I would always want a clutch between the engine and pump. Based on experience I've had far more pump/hose/hyd motor failures than clutch failures. Many of the failures if the pump were not clutched would have required shutting down the engine.

One clutch failure was the friction plates. No need to shut down the engine. The other was the drive between the engine and clutch. No immediate need to shut down the engine but we did to remove the failed parts as soon as it was reasonable to do so.
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Old 03-10-2020, 07:01 AM   #9
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And remember , if a hyd system starts to leak while in operation ,

DO NOT put your hand over the leak, 1500 or 3000 PSI can easily puncture your hide and HYD fluid in the blood can be rapidly deadly.
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Old 03-11-2020, 12:41 AM   #10
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Thanks for all of the great advice. Some questions:

1) There has been some concern about the rapid loss of hydraulic fluid and the inability to easily shut off the pump without a clutch. Not being a fish about, my boat's hydraulic system doesn't hold that much fluid. At its normal flow rate, it would be dry in about a minute. It is unlikely that it would discover the leak and shut it down (clutch or no clutch) in enough time to head off that disaster.

2) If the pump fails, it is isolated by check valves. Won't this keep it from affecting the rest of the hydraulic system? Let's say the pump just stops working -- the engine is driving it but there is no pressure coming out of the pump, that doesn't seem like a problem.

3) I agree it does look like a big hassle to unbolt that thing, lash it off to something clear of the shaft, and then install the cover plate. But, given the check valves, I don't think I would need to detach any hoses, yes?

I still haven't decided. The biggest reason, IMHO so far to not do it is the expense of reworking the system. I'm getting more comfortable with the lack of a clutch. Fish boats do this all of the time, American Bow Thruster (makers of my hydraulic system) also recommend removing the clutch.
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Old 03-11-2020, 04:17 AM   #11
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On a 57 NM are all hydraulic hoses easily visible for inspection? If not, once aged past 15 years it might be advisable to change out those unseen hose runs. Normally a leaky hose or fittings predates failure.

If you're having to add steering, hydraulic or transmission fluid suggest finding the leak and fixing it ASAP. There are additional leak potential items beyond the PTO.

Some years ago we were looking at purchasing a Nordhavn. Our preference was for electric thrusters and windlass for reasons raised by this thread. On our DF 48 only the stabilizers are hydraulic powered. All hoses and fittings are 100% visible during normal hourly ER checks. Art DeFever designed it this way intentionally.

On many vessels the hydraulic stabilizers themselves are buried from view. Not a good design IMHO and gets into the bad boats discussion raised in another thread. Some very notable brands are guilty of this mis-design.

Fortunately on our DF, if all else fails the engine with the PTO can be shut down. Twins!
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Old 03-11-2020, 06:52 AM   #12
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If you do need to replace a hyd hose install the screw in ends your self , so only hose needs to be carried as a maint item.

Be sure to purchase swivel end fittings for both ends of any hose.
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Old 03-11-2020, 06:59 AM   #13
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Misdiagnosis of the issue

Quote:
Originally Posted by mikehar View Post
Thanks for all of the great advice. Some questions:

1) There has been some concern about the rapid loss of hydraulic fluid and the inability to easily shut off the pump without a clutch. Not being a fish about, my boat's hydraulic system doesn't hold that much fluid. At its normal flow rate, it would be dry in about a minute. It is unlikely that it would discover the leak and shut it down (clutch or no clutch) in enough time to head off that disaster.

2) If the pump fails, it is isolated by check valves. Won't this keep it from affecting the rest of the hydraulic system? Let's say the pump just stops working -- the engine is driving it but there is no pressure coming out of the pump, that doesn't seem like a problem.

3) I agree it does look like a big hassle to unbolt that thing, lash it off to something clear of the shaft, and then install the cover plate. But, given the check valves, I don't think I would need to detach any hoses, yes?

I still haven't decided. The biggest reason, IMHO so far to not do it is the expense of reworking the system. I'm getting more comfortable with the lack of a clutch. Fish boats do this all of the time, American Bow Thruster (makers of my hydraulic system) also recommend removing the clutch.
The thing you are trying to prevent is burning up the hydraulic system by being able to stop the pump from turning. You dont Want the system turning without oil.

Or

Imagine experiencing ad I did my hydraulic oil getting hot and getting warnings on the user interface. it took some time for me to figure out why it was getting hot, but without a clutch, there is now way to disconnect the pump from the system. It is possible to burn things up. In my case, where I have two pumps and can electrically change from one pump to another, it might work to shut down the engine that is assigned to the pump.

If you have only one engine, well you are out of options.

What is the problem with the clutch?

Gordon
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Old 03-11-2020, 08:59 AM   #14
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Quote:
Originally Posted by mikehar View Post
Thanks for all of the great advice. Some questions:

1) There has been some concern about the rapid loss of hydraulic fluid and the inability to easily shut off the pump without a clutch. Not being a fish about, my boat's hydraulic system doesn't hold that much fluid. At its normal flow rate, it would be dry in about a minute. It is unlikely that it would discover the leak and shut it down (clutch or no clutch) in enough time to head off that disaster.

Let the pump run dry for very long and bad things will happen. Metal running against metal without lubrication will overheat. Very likely seize and damage who knows what as it tries to stop turning. Possibly, but not likely, hot enough to start a fire. Being able to disengage the pump ends that problem.


Quote:
2) If the pump fails, it is isolated by check valves. Won't this keep it from affecting the rest of the hydraulic system? Let's say the pump just stops working -- the engine is driving it but there is no pressure coming out of the pump, that doesn't seem like a problem.
You are probably correct, it would probably affect the system in the same way that de-clutching would. Hard to say without fully understanding your system.


Quote:
3) I agree it does look like a big hassle to unbolt that thing, lash it off to something clear of the shaft, and then install the cover plate. But, given the check valves, I don't think I would need to detach any hoses, yes?
There is no obvious reason to need to disconnect hoses. But you may not be able to move the pump without disconnecting. It would depend upon how long and flexible the hoses are.


Quote:
I still haven't decided. The biggest reason, IMHO so far to not do it is the expense of reworking the system. I'm getting more comfortable with the lack of a clutch. Fish boats do this all of the time, American Bow Thruster (makers of my hydraulic system) also recommend removing the clutch.
Interesting your remark about the fish boats. The fishing fleet is where I learned about a very reliable electric clutch, the Pitts Clutch. My experience was one clutch failure in over 20,000 hrs working the clutch a lot harder than you will be. We would engage and disengage at 1800 RPM many times a day to drive pump big enough to power a crane and multiple winches handling loads up to 2,500 lbs.


I would like to know why the thruster manufacturer recommends on clutch. They must have a good reason for it.



Back to your OP. What would the precious space be used for? In other words balance what you gain in space for something else vs what you loose in safety. And unless always in rough enough water to want the stabilizers on I could envision many hours where I'd want the hydraulics off. Hydraulic pumps do take a fair bit of HP meaning fuel to drive.
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Old 03-11-2020, 09:15 AM   #15
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Misdiagnosis of the issue

Quote:
Originally Posted by mikehar View Post
Thanks for all of the great advice. Some questions:

1) There has been some concern about the rapid loss of hydraulic fluid and the inability to easily shut off the pump without a clutch. Not being a fish about, my boat's hydraulic system doesn't hold that much fluid. At its normal flow rate, it would be dry in about a minute. It is unlikely that it would discover the leak and shut it down (clutch or no clutch) in enough time to head off that disaster.

2) If the pump fails, it is isolated by check valves. Won't this keep it from affecting the rest of the hydraulic system? Let's say the pump just stops working -- the engine is driving it but there is no pressure coming out of the pump, that doesn't seem like a problem.

3) I agree it does look like a big hassle to unbolt that thing, lash it off to something clear of the shaft, and then install the cover plate. But, given the check valves, I don't think I would need to detach any hoses, yes?

I still haven't decided. The biggest reason, IMHO so far to not do it is the expense of reworking the system. I'm getting more comfortable with the lack of a clutch. Fish boats do this all of the time, American Bow Thruster (makers of my hydraulic system) also recommend removing the clutch.
The thing you are trying to prevent is burning up the hydraulic system by being able to stop the pump from turning. You dont Want the system turning without oil.

Or

Imagine experiencing ad I did my hydraulic oil getting hot and getting warnings on the user interface. it took some time for me to figure out why it was getting hot, but without a clutch, there is now way to disconnect the pump from the system. It is possible to burn things up. In my case, where I have two pumps and can electrically change from one pump to another, it might work to shut down the engine that is assigned to the pump.

If you have only one engine, well you are out of options.

What is the problem with the clutch?

Gordon
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Old 03-11-2020, 09:28 AM   #16
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IMO, some folks would really want at least one PTO. I have none.
Get them fixed and enjoy life even more with hydraulic bow and stern thruster.
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Old 03-11-2020, 09:29 AM   #17
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I'm curious, is there any first hand experience of recreational vessel low hour PTOs failing with any regularity? My experience with PTOs on dirt moving equipment finds a pressure drop is the first indicator of imminent failure, generally at very high hours.

Hose failures are the real issue to be concerned about with marine age the more common reason.
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Old 11-11-2020, 01:22 PM   #18
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I forgot to follow up earlier, I decided to leave the clutch in place.

Thanks for the informative discussion!
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Old 11-11-2020, 01:30 PM   #19
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Quote:
Originally Posted by sunchaser View Post
Some years ago we were looking at purchasing a Nordhavn. Our preference was for electric thrusters and windlass for reasons raised by this thread. On our DF 48 only the stabilizers are hydraulic powered. All hoses and fittings are 100% visible during normal hourly ER checks. Art DeFever designed it this way intentionally.

On many vessels the hydraulic stabilizers themselves are buried from view. Not a good design IMHO and gets into the bad boats discussion raised in another thread. Some very notable brands are guilty of this mis-design.
I think the reliability and functionality of hydraulic thrusters vastly outweigh the initial complexity. Last week we were short-handed and being blown off of an unprotected dock at the boatyard. It was very easy to pin the boat against the dock with the proportional hydraulic thrusters. No fuss, no rush. No duty cycle to worry about. The same goes for the windless. Doesn't matter if I have 50 or 500' of chain out, the windless never gets 'tired'. As for being able to visually inspect every inch of the hydraulic lines, I think that is overkill. There are several indicators of a leak (reservoir level, pressure gauges). I'll go check out that thread!
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Old 11-12-2020, 12:49 AM   #20
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My pump interface is a bit different. I do not know its pros and cons. The pump for my stabilizers is mounted to the front of one of my Lehman 120s. The interface is a rubber coupling similar to that shown in the picture. I am able to decouple the pump in five minutes by removing four mounting bolts and sliding the pump away from the engine. This must be done whenever changing alternator belts.

I am aware of the trick to wire tie a replacement in place. I do not like this idea as the belt will dry out and become brittle with age and heat. I keep a spare that I vacuum-pack with a Food Saver. Plus, that engine is double-belted.Click image for larger version

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