I would like to share some information concerning one of the most important accessory on our boats, the autopilot, in my case the ST 6000 from 1999.
Last summer I heard some disturbing sounds coming from the drive unit. It was obviously a kind a grinding noise you get when mechanics are not sufficiently lubricated.
Therefore I excessively sprayed some lithium grease on the out sliding arm that turns the quadrant, hoping the grease would find it's way to where it was needed. Wrong assumption, I had to find out afterwards.
A month ago I was on the boat for a few weeks and decided to address the problem in a "professional-do it yourself way". I'm aware of the prophetic rule "if it ain't broke, don't fix it ", but my philosophy has always been the kind of the preventive maintenance, and in this case I don't want the AP to let me down when crossing the Atlantic.
So disassemble the unit and do a proper grease-job was the name of the game.
Easier said than done, I was unable to get the cast-iron or is it cast-aluminium alloy back cover off to get an understanding on how to dismantle the unit so I could reach the actual non-lubricated parts. That cover is held to the rest of the unit by 4 cornered allen screws, and eventually I found out that also 2 long brass bolts kept the cover on, but that was after I messed up.
You must understand the unit was on location as the electric wiring was still attached to it.
Therefore I wanted the solid cover off to disconnect the leads and take the unit to a more comfortable place on the boat .
At that point I had no clue on how to get the cover off so I thought of working around it and try to get the out-sliding arm off in order to grease the driving mechanisms. I searched the internet but strange enough there's little or nothing be found on the matter.
Now there's a lot of parts involved of which I don't really know how they're called, so I hope you can bear with me on my used terminology.
Long story short, I got the cap of the main pipe off, pulled the arm completely out until it jammed and could see the drive is a combo of worm and worm-holder. By pulling harder (I wanted that worm-holder & arm out of the way) and in my enthusiasm to get this job off my bucket list I managed to pull the lot out and so came a bunch of bearing balls too. They flew in every direction, in holes, in gaps, straight down to the bilge.
It's one of those awkward moments you realize you're in trouble, and that's putting it mildly.
Drastic times call for desperate measures, I just cut the wiring and took the unit to the OT (operating theater) inside, the saloon.
Let me explain with pictures and some guiding comments under each pic.
Exploded view of the autopilot, unfortunately no explanation / indication of the actual worm-drive itself.
This is where I started, remember it was this inner-pipe with attached worm-holder I was desperate to pull out with a fireworks of bearing balls as a result.
The main pipe with worm inside, on the top/end a groove for the circlip that gave away.
The worm-holder , and if you look close you can see a few bearing balls here and there, I managed to retrieve some more, but the rest is to be found in the bilge somewhere.
Very interesting pic this is, the main pipe, and notice the red arrow, that's the spot where you can find a small hole. Yes ....... a hole to spray in some lubricant. I missed that one, silly is it not.
Up to date I still don't know how this main pipe is fixed to the unit, if I could gotten that off that would of saved me all the work that comes next . I tried everything, most likely it's screwed on/in , but I didn't want to press my luck by using brutal force to unscrew it.
Also notice the long brass yellow bolts holding the heavy back cover in place together with the 4 corner allen screws.
The back cover
Again a very interesting picture , the worm-holder and the ' recirculating bearing '. Never heard of it before, but in this type the bearing balls are continuously in a loop of circulation and are being prevented to escape. See one of the next pics.
The back cover off with a nice view on the actual drive itself.
Very ingenious system , but that goes for the complete autopilot.
Center view is the solenoid that commands the drive-section and consequently the position of the rudder by pulses of the CPU in conjunction with the date from the flux-gate compass.
Another thing to worry about , notice the left-hand corner next to the solenoid. Drive belt debris, need I say more.
The drive belt specs, another spare part to have on board I guess. Suggestion : don't buy Raymarine's, unless you don't mind paying 3 to 4 times more than this easy over the counter obtainable small belt - For Example.
I'll focus on the drive-section itself now because that had come off so I could get the worm out and re-unite it with the worm-holder.
Clock work mechanics, the planetary gears. 2 dowel pins hold this 'contraption' on the worm.
Some explanation on the planetary gears, they run on the little axles no bearings involved. Big problem, due to a lack of grease they will wear down and will make a rattling / grinding noise. Maybe something to think about when hearing a suspicious sound coming from the AP.
Lubricating this part is fairly easy, take the back cover off after you get the front cover out, grease the worm (through the little hole remember) and also spray some lithium on the little gears, no harm no foul. I make sure to, at all time, have my supply of 3 in 1 lithium grease on board.
Worm's out, more to come.
When this was done, I was back in business. Get the worm back in from the other end and mount the worm-holder with it's recirculating ball bearing.
Before sliding the worm-holder on it had to be separated from the inner-pipe. If not I would not succeed in getting the circlip (the one I mistakenly pulled off) back on to keep the holder on the worm. The inner pipe is just screwed on.
Also have a look at the re-circulation loops. They're in 2 parts and each side of the worm-holder carries a set. Notice the small lips on one side of half a loop, this is what keeps the bearing balls in the loop. When the worm-holder slides over the worm the balls are pushed in a direction and the lips will force them to enter the loop again. Great stuff.
The circlip that nearly gave me a heart-attack is ready to go home again .
First fill the worm-holder with bearing balls and make sure it completely loaded. That's done easy by pushing balls in one hole and gently sliding the holder over the worm until the balls appear on the exit of the other hole. Re-do that a few times so the channel is full.
Then fill the loop itself and stick it in the holes and fix it with the bridge that holds it in place. The whole procedure is to be repeated for the other side.
As for missing bearing balls, I never went looking for them in the bilge, my wife was able to get some from the local bike store. The size is 3 mm. So my end is well, all is well.
Once the circlip was on the inner pipe was screwed back on and so was the end cap on the main pipe.
Eye bolt (to put over the quadrant pin) in place.
Getting the other side assembled.
Leaves me to get a new belt on when we get back to the boat.
I see this project as a blessing in disguise, my mistake by ripping the thing apart to start with, gave me a chance to understand how it really works, might come in handy later, although I hope it never has to.
That's it gentlemen, it's clear that our Autopilots do need a minimum of maintenance, better safe than sorry.
Sailbleu - Sun Odyssey 40DS
Editor's note: Republished from an original article from Jeanneau Owners Forum
PDF Download for the Raymarine Service Manual for the ST 6000 /ST 7000