What steering system is ths?

1974 Gulfstar Trawler - this is the hydraulic steering reservoir, at the lower helm station. Notice the air pressure pump in the foreground, the air pressure gauge, and the air pressure bleed-off valve (looks like a bike tire valve) in the center). I'm guessing it's some kind of pressurized system!

Questions:
1. What brand is it, and model?
2. What should it be pressurized to? (What psi?)
3. What fluid should I use to to top it up?

Thanks!!!
(I can't figure out how to insert a photo, so I've attached it. Hope that works!)

Looks like a hynautic unit, i usually pressurize mine to 25 PSI.

I keep the pressure between 25 and 30 PSI and use Shell Tellus oil. My manual warns against using ATF.

The book recommends Hydraulic oil, at $25 per qt at West Marine or $18 per gallon at the local airport.

Y pressurized?

Atf , works, pressure reduces air bubbles in the lines. It also helps if bleeding is required. Usually air can be bleed by rotating wheel 100 revolutions each way.

My Hynautic shifter tank is book recommended to be in the 90 psi range. I seem to recall coolant rather than oil in some of these systems.

meridian said:

The book recommends Hydraulic oil, at $25 per qt at West Marine or $18 per gallon at the local airport.

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Or $8.50/gallon at Tractor Supply.

As always, great replies from the good people on TF!!!

I'll head to Tractor Supply for some of that good $8.50 per gallon stuff tomorrow, and pump it up to 25 psi.

Thanks!

Couple years ago my air pressure dropped to zero over the winter .the first time out for the season and I didn't check it . I was completely out of slip before I realized it, and yes the wind was blowing . Crowded Marina with wind blowing , no steering and single engine and the first time my grandson was on the boat . All turned out well and we were able to maneuver boat into an empty slip . I always check air pressure before leaving dock now .

sunchaser said:

My Hynautic shifter tank is book recommended to be in the 90 psi range. I seem to recall coolant rather than oil in some of these systems.

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Coolant is used in the shifter systems. Hydraulic fluid is normally used in the steering systems.

BrianSmith said:

1974 Gulfstar Trawler - this is the hydraulic steering reservoir, at the lower helm station. Notice the air pressure pump in the foreground, the air pressure gauge, and the air pressure bleed-off valve (looks like a bike tire valve) in the center). I'm guessing it's some kind of pressurized system!

Questions:
1. What brand is it, and model?
2. What should it be pressurized to? (What psi?)
3. What fluid should I use to to top it up?

Thanks!!!
(I can't figure out how to insert a photo, so I've attached it. Hope that works!)

Click to expand...

I think you have an air pump built into that tank.

Capt Bill called it correctly, the knurled knob is a pump. I would not use it because the seals may be old and opening and using the pump may leak after pumping the reservoir up. Not good.

The pressure pushes oil up to the helm, and you lose pressure and you lose steering. Previous posters are correct, the Hynautic controls use glycol, the steering uses light hydraulic oil, not ATF.

I have never been a big fan of pressurized steering systems. I know there are plenty out there that will now defend their 30 year old Hynautic systems, but to me it's just one more thing to fail, and steering is kind of important.

I would consider replacing the helm(s) at the first sign of a problem. That looks like a very old version, and the aluminum components don't always do well below deck. A Sea Star system is not pressurized, needs no reservoir, is compatible with your actuator (ram) and even if its leaking as long as you pour some oil in it you can steer yourself home.

Hynautic and Sea Star are both owned by the same company, and there is still support for your system, take a look here:

SeaStar Solutions

My $0.02

My Hynautic system is only 15 years old, looks just like that, and works great. If it's bleeding off it's pressure, it's probably the "O" ring in the fill cap for the reservoir. I can see no reason to spend money to fix something that's not broken. It's another simple check before getting underway daily and is unlikely to "suddenly" lose it's pressure, being far more likely to gradually bleed off. If there is a leak anywhere in the system it will show up on the pressure gauge.

You might get more information on your system to get psi range, mine is to range from 15 to 20 psi. Don't have a clue what brand mine is just note from po.

We have 1984 Silverton with this same Hynautic system. Here's a link to a scan I made of the manual for it.
http://aventusllc.com/dalewindle/Hynautic Steering System 1984.pdf

I don't think there will have been many changes to the system from 74 to 84.

Hope this helps a bit.

Dale.

Mine is around 35 psi.


Mine leaked down from a weep on a fitting back near the ram.


Mine is 28 years old and while I worry about the copper tubing snaked through the bilge, I don't worry about the other components more than any other form of steering I use whie boating both for pleasure and work.


The Sea Star unpressurized system on my assistance boat has had the o rings fail and it is much newer....while I don't fancy loosing steering...driving a single engine vessel I got other systems to worry about...or not.


If and when the time rolls around to replace the system, yes simple usually is better.

Another Hynautic manual I just found.
http://www.whitbybrewersailboats.com/maintenance?download=52:hynautic-owners-manual

Dale

Don't get just any tractor hydraulic fluid, it's too thick. The hynautic fluid is MIL 5606 aircraft hydraulic fluid, thin stuff.

Dale (windled),

Thanks for the manuals - those give me all the info I could ever want, I think! (Including verification of the spec for the hydraulic fluid suggested by Ski in NC - thanks!)

I love Trawler Forum - what a fantastic resource.

Ski in NC said:

Don't get just any tractor hydraulic fluid, it's too thick. The hynautic fluid is MIL 5606 aircraft hydraulic fluid, thin stuff.

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Good catch Ski

I just learned something.

I have the Hynautic unit on my Gulfstar and have the original 40 year old manual! It calls for 20-30 PSI and MIL-0-5606 aircraft hydraulic fluid or type A transmission fluid in warmer climates.

UPDATE: I looked at a couple of auto parts stores, and Tractor Supply, and found hydraulic fluid that didn't have sufficient details on the label to know if it would meet the specs. So I passed on those, went to West Marine, and paid $27 for a quart of the SeaStar fluid that says "Hynautic" right on the label. (I later found it online for about $18 / quart, but don't know if that included shipping.) Next time - if there IS a next time (the fluid really shouldn't ever go away), I will investigate some aviation hydraulic fluid that meets MIL spec 5606, and see if I can fine some for less $$, but I was in kind of a hurry this time - got a Bahamas trip coming up fast!

Oh - I'm pretty sure the PO used Dexron ATF in this unit - what's in there is red, and the SeaStar fluid is almost clear. It seems to have worked just fine for a lot of years.

If you buy the aircraft fluid, it is red like ATF. Dyed that way so pilots/mechanics can tell the difference between a drip that is fuel or hyd.

You can use ATF, but because it is thicker it takes more effort to turn the rudder, especially if turning fast and if it is cold.

I like the crisper feel using the 5606 stuff, and up here I often run in the winter. Fla, not much of a difference likely.

My Prairie of 1979 vintage has the Hynautic system installed. It has the same stiff steering as a previous boat years ago. I disconnected the ram from the tiller to isolate this stiffness. The rudder swings free and the stiffness remained. I was told this is normal. Is this truly normal?

there may be some transfer valves that are gummed up.