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Old 04-26-2015, 02:40 PM   #21
City: Hotel, CA
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Originally Posted by Ski in NC View Post
Don't get just any tractor hydraulic fluid, it's too thick. The hynautic fluid is MIL 5606 aircraft hydraulic fluid, thin stuff.

Good catch Ski

I just learned something.


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Old 04-26-2015, 07:23 PM   #22
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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.
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Old 04-28-2015, 08:48 AM   #23
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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.
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Old 04-28-2015, 09:12 AM   #24
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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.
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Old 11-30-2015, 04:57 PM   #25
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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?
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Old 11-30-2015, 07:20 PM   #26
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there may be some transfer valves that are gummed up.

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