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Old 04-26-2019, 04:32 PM   #1
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Need help diagnosing stabilizer whine

I have developed a whine in my Naiad stabilizers. It takes a few minutes to develop after they are turned on, and is quite noticeable. I have changed the oil and installed a new filter. Also checked for loose fittings and changed the belt on the hydraulic pump.

Anybody experienced this before?
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Old 04-26-2019, 04:50 PM   #2
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Where is the wine from Pump, Gyro, etc. Also had a similar squeal /whine from the fan belt. A single fan belt is not enough for Naiads, they really need a double belt drive. I converted mine on my last boat to a direct drive from the front pulley , solved all my problems. Craig at Stabilized marine carries the parts. The only down part of the conversion is disconnecting the drive if you burst a hose or similar.
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Old 04-27-2019, 10:37 PM   #3
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Martin, thanks for the reply. I changed the belt but it made no difference. After doing tons of research it appears that I have a cavitation issue, probably caused by a blockage between the pump and the reservoir. After looking at the system drawings in my owners manual it seems there is a strainer located inside the reservoir. I have sent off a email to Naiad but will need to wait until Monday morning for a reply.
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Old 04-28-2019, 02:11 AM   #4
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I have not had a boat (or even operated one) with stabilizers. But I have worked on a fair number of similar hydraulic systems on vehicles, tractors, and construction equipment over the years - diagnosing problems, rebuilding pumps, hoses, racks, etc.

1) I interpreted - and maybe I was wrong - Martin's comments to imply the pulley shaft was overloaded in this application, and the noise might not be the belt itself, but accumulated wear on the shaft or bearings in the pump. So once it's worn enough to whine, a new belt isn't going to change things, and only rebuilding the pump and re-engineering the pulley so it didn't wear as quickly again. Or maybe I misunderstood his point.

2) You can isolate the noise using an improvised stethoscope (or a real one). A large screwdriver is adequate, or any solid rod like that. Put one end on various parts of the system (pump, at the stabilizer, etc.), the other on/next to your ear against bone. You will hear the noise transmitted through the system, but when you are at or close to the problem it will be very pronounced and obvious. This can neck down your problem considerably.

3) Again, I know nothing about the Naiad system in detail. I tried to find a diagram of the hydraulic circuit from a google search but oddly, no success. Maybe something is unique to this system, but it sounds really unlikely or at minimum weird to me there would be a blockage develop in the low-pressure part of the system between the reservoir and the pump. That is, overall, the very least stressed part of any hydraulic system.

4) Using some physical reasoning and your comment that the whine takes a few minutes to develop, it leads me to put wear and not blockage/constriction as a higher probability in a differential diagnosis. I say this because the pressure in the system is consistent after the first few revolutions of the pump onward. A cavitation/starvation issue should be apparent right away. What does change over a few minutes throughout the system is temperature. This has two main effects a) greatly thinning the fluid, and b) increasing tolerances in components from thermal expansion. Either of these, and especially the combination, can create a noise as metal now contacts metal unlike when cold. Of the P,V, and T in a fluid or gas system, it seem to me that since P and V (assuming the system is full and not leaking or you would have said so) have no effect on the noise, and T appears, to, I think about what that implies.

As I said, I've worked a bit on similar systems and PTOs, but all are unique and I don't know this system.
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Old 04-28-2019, 08:56 AM   #5
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I think Ciivilitas has the answer to locate the whine area and where it's coming from first to diagnose the problem.
My problem was strange with the belts when the belt is new one belt can just handle it but any minute slackening or heating of the belt when the engine room heated up, started the belt squealing. I installed forced air and extractors in the engine room, helped a bit but the conversion to direct drive pump solved it.
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Old 04-28-2019, 08:59 AM   #6
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Civilitas:
Thank you very much for your insight. I agree that it could be air leaking in at the pump shaft. There is no kind of clutch on the pump so when the engine starts the pump starts rotating immediately, but it is bypassing the fluid back to the reservoir at a low pressure. It is not until the control switch is moved to on does pressure build in the system. Yesterday the whine did not begin until approximately 5 minutes after the switch was turned on.

I have a stethoscope and have listened to all the components, the noise is at the pump and in the outlet hose leaving the pump.

The reservoir is above the level of the pump and the fluid is gravity fed to the pump ( as all systems should be). Anything impeding the gravity fed fluid to the pump will starve the pump and it will cavitate, causing a whine.

So I believe either air is being introduced into the system, or the pump is starving for fluid
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