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. I’m 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 it’s 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

seized pump could cause major damage if not disconnected.

Terry

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.

If the PTO clutch is not reliable , replace it.

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?

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.

Ted

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.

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.

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.

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.

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!

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.

Misdiagnosis of the issue

mikehar said:

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.

Click to expand...

The thing you are trying to prevent is burning up the hydraulic system by being able to stop the pump from turning. You don’t 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

mikehar said:

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.

Click to expand...

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.

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.

Click to expand...

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.

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?

Click to expand...

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.

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.

Click to expand...

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.

Misdiagnosis of the issue

mikehar said:

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.

Click to expand...

The thing you are trying to prevent is burning up the hydraulic system by being able to stop the pump from turning. You don’t 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

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.

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.

I forgot to follow up earlier, I decided to leave the clutch in place.

Thanks for the informative discussion!

sunchaser said:

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.

Click to expand...

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!

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.

"I think the reliability and functionality of hydraulic thrusters vastly outweigh the initial complexity."


YOU BET! a Hyd windlass if overloaded simply stops , no harm , no white smoke , no failure!

mikehar said:

I have a 57’ Northern Marine trawler that has a pto on the main and one on the gensets. Both PTOs have a clutch. I’m 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 it’s 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

Click to expand...

Does your vessel have a hydraulic drive get home setup? If so the original design may require the clutch set up. One of the former NM guys from around Anacortes could offer some design and setup history maybe.

BTW, the NM 64 is one of my favorite vessels. Do you have both a 64 and 57?

My hydraulic pump is a swash-plate pump, same as in your hydraulic steering system. The swash plate in the steering is fixed.

I have a hydraulic solenoid that I use to start the system; turning on the hydraulics to run the windlass or the crane opens a solenoid valve and the lowered pressure deflects the swash plate and it pumps. The plate varies its angle under demand and pump speed (engine) to provide a constant flow and pressure for the systems. The pump always runs with the engine but the pump is just spinning the swash plate. A failure of a line will not cause the pump to fail and if I detect it, close the switch and the pump continues to turn but it stops pumping.

Theses pumps and systems are much better than clutches but of course, the manufacturers went for the cheapest solution. The swash plate pumps are common aircraft pumps and in fact, mine is made by Cessna.

Your system must have external pressure and flow regulators? Mine is all done by the pump.

I was a commercial fisherman and used hydraulics for my anchor winch and fishing gear. The pump ran off the main and used a clutch. Running to the grounds required no hydraulics and clutching off the pump saved ever needing to rebuild it.

Cruising you only need hydraulics docking and anchoring. Removing the clutch means the one piece of the hydraulic system that sees the most wear, the pump, is running all the time you run the main. Unless your cruising is short jaunts, the pump is getting many times the necessary wear. Another issue is seals can fail on the pump, valves and motors. Without a quick shutdown option, hydraulic oil can get in the water. A commercial friend had a deck leak in port while working below. The fine was $2000.