Hydraulic steering, what hose to use?

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Jan 20, 2016
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Custom Built
Last year I got my steering cylinder rebuilt as it was leaking. Seals were changed, rod was polished clean and everything was fine.
After a winter on the ground I noticed again some leakage. This time it is not the cylinder itself but the fitting connection. The leak is very tiny, but after 6 month on the ground it was clearly noticeable.
My setup is as follow:
From the helm the line is copper.
Between the cylinder and the copper line there is around 1 foot of hose, quite stiff but less than the copper line.
Fitting on this hose, both side is compression fitting with olive/ferule. And this is where the leak is.
I am not sure if the fitting on the cylinder is NPSM or compression.
To illustrate what I mean here is NPSM fitting:


And compression:


So the questions...
First: Is compression fitting common for hydraulic? Is it the right thing?
Second: Any advice on getting this leak free?
Last: any recommendation on hose to be used? I found a lot of different hoses that could fit.

Whe I was building boats where failure was not an option, it was Aeroquip hose and fittings.
I have the same setup, but found that all fittings were leaking due to missing inserts in the copper pipes.
Try loosening, two wrenches, the ferrule nut and then wiggling it as you resnug it up. THis hopefully will align it better. Once snugged then use two wrenches to tighten the nut fully.
The two wrenches are often needed to turn only the nut. If the whole thing twists you may monkey the fitting and tube so it can't be fixed.
Generally compression fittings are not a good bet for use in an application like this. Although a low pressure hydraulic system they can still see up to 1,000 psi. Compression is usually used on much lower pressure.

You do not need the two types of fittings you showed. They are high pressure fittings, expensive and not common.

If the copper tubing is in good shape then consider purchasing a DOUBLE flaring tool and learn to use it. It's not hard. A few practice flares with some extra tubing will do it. That will produce a good seal. Just be sure to put the nut on first before forming the flare.

Then other fittings can be adapted easily.
YOu might be able to adapt the hose end to the new flare with the right fitting.
Without seeing this it's kind of hard to say how to do the repair.
My own system is copper tubing, flare fittings using a double flare tool and it has been leak free for 40 yrs with a few exceptions and those were single flairs that were poorly done and cracked.

For new hose talk to your local hydraulic shop. A working pressure of up to 1,000psi should be more than enough. THere is very little movement of the hose so a hydraulic hose like this will still be flexible enough.

Some photos of what you have?
Lou, I have been around a lot of hydraulic fittings, and I don't recall ever seeing the type that you posted. If they are used only at the rudder cylinder, consider going to a hydraulic shop and getting new fittings that are industry standard. They can make up the hoses for you too. Aeroquip is fine, but so would anything that meets spec for 1000psi oil.
Thank you guys, I think I will pass by the shop that changed my cylinder seals last year to ask them to provide me with two hoses.

I used hose normally used for front-end loaders. It’s orange, and much bigger than the shiny and small black hose usually used.

Used a oversized steering pump and slave cylinder too. Was looking for stuff that wouldn’t fail in Alaska.

Everything worked well and I’m set up for 3 turns L to L. Due to the fast steering, large shafts and seals and other oversized components I do have a little more steer effort required than for most boats this size.
I dont like olive ferrule compression tubing fittings much at all, they want to leak, low pressure water systems seem ok sort of with them. It is how they built my boat back in 1970 using all annealed copper tubing, which I have maintained, mainly cause copper kills bacterias, and what I have works.

Flared made for hydraulic type fittings are what you want.
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