Hydraulic steering with autopilot pressure question

[O'Motorboater]

Hi everyone,

I was doing some poking around on my new to me Bayliner 3388 and happened to take a look at the pressure gauge on my Hynautic hydraulic steering system reservoir and noticed that it reads at 5 to 7 PSI currently. According to the label on the reservoir it should be 25-30 PSI. However, I did a little research and found that some autopilot systems require a lower PSI of a say around 10 PSI. I do have a Raytheon ST5000+ autopilot but can't find anything in the manual pertaining to steering system pressure. So I'm now wondering if its lower because of the autopilot integration or do I just have a leak. Steering does function but it does seem to take a little more effort than I'd expect and it feels a little rough, not super smooth. I am tempted to just pressurize it to the label's specifications and see what happens, but don't want to do so if it's where it should be given the auto pilot. Any thoughts or info would be greatly appreciated!

Thanks.

[capnken]

I would pressurize main reservoir for steering per Hynautics recommendation to 25-30. can't remember but think procedure is to add fluid after depressurizing and then pressurize with sport or bicycle pump...sorry I can't remember more...also look for signs of leaks at helm and see if any air in system....you may need to bleed air from lines if helm control doesn't give you full rudder travel...good luck, and if you have leaks seal kit is cheap, think they sell on Amazon...if I remember right there's a good Youtube on seal replacement. Also don't remember a separate reservoir for auto pilot....

[higgins_jr]

I run between 15-20psi to not put too much pressure on seals etc and it runs fine. I find that a 12v compressor pump with a “flip” lever on the hose head works best vs a screw on bike pump connection hose. I can’t seem to get the bike hose connector unscrewed fast enough without loosing much of the pressure.

Have fun! Cheers

[capnken]

I would stick to Hynautics reommendations. I rebuilt helm stations and seals are robust. Sorry you had trouble with hand pump but I have found it requires very little effort or pump strokes to pressurize reservoir and you have much more control with small hand pump..(also remember when reservoir is filled to recommended level there is a relatively small volume of air to pressurize.)...would also recommend you check pressure several times after to confirm system is holding pressure

[tom]

In my experience, it should be pressurized to OEM specs with or with out an autopilot. Maybe bring it to 15 psi after filling fluid and look for leaks then go to 30. Sometimes is the oring under the fill plug.

[MacPhid]

Do you have Hynautic fluid in the system or has it been changed to ATF? ATF will give rough operation in cooler weather, and more steering resistance the colder it is. Lots of boats went to ATF due to cost when refilling, mine included unfortunately. I'd love to purge it all and go back to the proper fluid. Perhaps when I upgrade the auto pilot

James

[O'Motorboater]

Fluid type is an interesting thought. I wasn't aware that would make a difference. I don't know if it has the Hynautic fluid or ATF honestly. Is there an easy way to tell? The fluid in the sight class looks dark in color, but that could just be the way the sight glasses look. I know ATF is red usually.
I think based on what's been mentioned here so far is I'll add some air and see how it goes for a start. Thanks to everyone so far!

[higgins_jr]

Yes, the sight glass can be hard to tell the color.

If you’re planning to add air then you can let the pressure go via the air valve on the top of the tank. Remove the cap/stem and stick a clean wire coat hanger in there to see the existing color. If red ATF, but I suspect, like mine where the sight glass looked dark, it should be the real stuff. Then you have to repressurize the tank/system!

Or shine a strong pencil torch in the sight glass to see if that helps!

Cheers

[O'Motorboater]

Ok. Thank you!

[MacPhid]

If you do depressurize then the fill port can be removed, it's got an o-ring seal so easily replaced. With the fill cover removed you might be able to clean the sight ports with a long handle cotton swab. Then you'll be able to see if it's ATF fluid. I remember reading that the bottom valve block should not be uncovered, but can't say for sure that's the case.

James

[capnken]

the most important consideration is that Hynautics calls for a MINERAL OIL, which is what is used in their system. The seals are specifically designed for mineral oil and if you use other types will degrade....saw the result of wrong fluid in a power steering unit and the seals literally dissolve. ATF has the right viscosity and works fine in the systems. PS...the bleeding procedure if you rebuild helm involves turning helm back and forth to end alot of times and I was about to give up on bleeding mine and it suddenly felt 'hard' and rudder reacted...took more turns than called for but as I said make sure you confirm when done that reservoir is properly filled and no pressure loss, and that you can achieve full rudder travel. My 45 is a 1989 and I would expect that after 30 years most Hynautic systems will leak and require rebuilding like mine...watch for leaks if you have an older boat!

[O'Motorboater]

Thanks again everyone. Lots of good info and direction. As always the knowledge is greatly appreciated.

[RDOIII]

One added comment is from the experience I had when adding air pressure to my system. Several years ago I tried to add pressure to the system. Using a bicycle style pump I was able to increase the pressure to where it should be. BUT, upon removing the pump hose. all the pressure released through the air valve. I tried several things to fix the seal to no avail. I was away from my marina and out of commission. Fortunately the air valve is a standard air tank fitting. I was fortunately in a town with a hardware store. They had two replacements which I bought. Suggest getting a replacement before trying to add air to avoid a like dilemma.

[O'Motorboater]

good idea, might just be worth replacing the fitting or valve core to rule that out.

[Jmason]

Sunrinner
my bike pumps & my battery powered pump have a flip release connector. Pump and flip the release. No loss of pressure at the valve.
I check the pressure at the gauge (which may be inaccurate). Check the fluid if necessary I add fluid, pressurize, then rotate flybridge wheel a couple of port to std turns, pilothouse same, check pressure and fluid, correct if needed. Hynautics manual explains process.
1990 4588
Port Hueneme Ca

[Quig]

Hello folks,
I have a similar system on my 4788. Something many people do not know is that the pressure in the steering system reservoir is NOT utilized to make the steering function - either manually or through autopilot. The system reservoir is pressurized ONLY because it is located somewhere OTHER than at the highest point in the system. If the reservoir were at the top of the system (let's say up on the flybridge), there would be no need for it to be pressurized and gravity would enable the fluid to flow down through all the pipes. The air pressure above the fluid level in the reservoir merely pushes the oil UP through the system. The pressure gauge is a way for you to tell if you have a leak in the system. Keep an eye on the gauge - if it drops, there is fluid leaking out of the system somewhere. The pressure recommendation is a guideline only (more related to the rating of seals in the system) and does not affect the system operation.

Cheers
Leo

[joe440]

Hynautic 3 line bleed. Talks about oil, air pressure, and how to bleed the system.

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKE wjVt6je4ZH_AhV_GjQIHYkUDsIQFnoECAgQAQ&url=http%3A% 2F%2Fwww.boatsteer.com%2Fassets%2FHynautic_MS_Purg ing_Instructions.pdf&usg=AOvVaw3PLoHmfXAkfUtAjGomL I2B