Service: Omega Seamaster Professional Planet Ocean 168.1665 / calibre 8500

IMG_3090I’m sure most of our readers are as curious as I was to get my hands on an 8500 movement for the first time. I had of course seen one before, but so far, no service had been required. So I went out and bought myself a 1 1/2 year old Planet Ocean with box and papers in order to have a good look.

Before opening it, I do a bit of testing. I get a 67 hour 50 minutes power reserve, and that is impressive. The two barrels are doing their work it seems. In terms of accuracy, I am disappointed, as the watch gains 4 to 5 seconds per day, and not at a constant rate. I expected much better from a 1.5 year old 8500.IMG_3088

This is the timegrapher image, and now I’m not too surprised any more that the watch isn’t keeping good time. My Rolex that I serviced 2 years ago looks much much better than this.IMG_3125

The movement is beautifully decorated, and has a balance bridge instead of a balance cock, just like the Rolex 3135.


Some microscope photos with details. Here the new in-house shock protection.0925085633

The decoration is nicely executed.0925085714

Lovely detail of the “39 Jewels” writing.0925105458

Some dirt under the barrel, which I feel shouldn’t be there after 1.5 years.0925105523

No idea what that stands for, but somebody here might know?0925105538

Very well executed Omega stamping.IMG_3129

The auto winder, which is of course bi-directional. A wire spring holds the wig-wag wheels in place.IMG_3130

The back of the dial has a fingerprint. Must be Swiss ūüėȬ†IMG_3131

I like the orange numbers – good looking dial.IMG_3132

The movement is not small. The diameter is 29mm (29.5mm of the step), and the height is 5.5mm. So no chance of ever fitting this into a more elegant watch, which is a shame.IMG_3133

The Silicon (silicium) balance and hairspring. Great stuff, as it’s a lot more temperature stable, and adds to the accuracy of the movement. At the top, there is a brass screw to adjust the height of the bridge on once side to adjust the end shake of the balance. The Rolex 3135 has that as well, but it can be adjusted on both sides so that the bridge is always parallel to the plate.IMG_3134

A first look at the co-axial escapement. IMG_3137

The pallet fork and escape wheel are visible here.IMG_3142

Very nice construction with the two barrels. One barrel contains a manual mainspring (I measured 1.17mm x 0.095mm x 340mm), and the right barrel contains an automatic mainspring (I measured 1.49mm x 0.08mm x 400mm). The manual mainspring is weaker than the automatic one, so it will wind fully first, then the automatic spring is wound until it starts slipping in the barrel. A lot better than other long power reserve movements with only one mainspring.IMG_3147 IMG_3148

The barrels and their springs.IMG_3149

There is some chipped off stuff at the bottom of the barrel, and I wonder if it’s the famous DLC (diamond like coating).IMG_3150

The automatic mainspring has of course braking grease applied to it, which does look already a bit dried out.IMG_3151

The top plate.IMG_3152

Now, let’s have a peek under the bottom plate.IMG_3154

Fairly straightforward construction with nothing outstanding to be seen here.IMG_3157 IMG_3163

Everything gets cleaned.IMG_3164

I start off with the two barrels. The automatic barrel gets a light coating of braking grease.IMG_3165

Then the balance jewels go back in.IMG_3167

Here you can see how the winding of the two barrels is linked.IMG_3168

The gear train goes in. You can see the hacking lever at 9 o’clock.IMG_3169

A very ETA looking setting/winding mechanism.IMG_3172

And yes, astonishingly, the movement really did need a service after 1.5 years! The movement is slightly slow, but I can’t get hold of the special tool to adjust the balance. I have ordered it, and I should get it within the next two weeks for a mere ¬£300.IMG_3174

Now the bottom plate comes back together. There is no quick-set date, but the hour hand jumps from hour to hour in the first crown position, so you have to go through 24 hour clicks to change the date by one day.¬†That’s quite normal for movements that have an hour jump function, as that works on the first position, which is otherwise used for the quick-set date.IMG_3178

Super jeweling, and a delight to look at.IMG_3179

The date change is anything but snappy. You can see here that the 22 is already going down to make way for the 23, without the date changing over. It’s a very standard ETA type date wheel, and a bit disappointing. The Rolex 3135 date change mechanism is a pure joy to look at, and by far better than this.IMG_3181

Dial and hands are on, and we are ready for casing.IMG_3182

With a new case back gasket, the watch is almost serviced.IMG_3183

Nice looking watch, but very very high – 16.2mm!

So, what do I make of it?

I love the look of it, the decoration, the jeweling, the silicon balance and hairspring, the accuracy (once it’s serviced again), the two barrels and the power reserve (even though I’m not quite sure what I need that for).

I don’t like the slow and cheap date change, the fact that I had already dirt under the barrel and that the movement needed a service after 1.5 years, and the height of the movement. It’s made for chunky watches, but it would have been nice to see this in a more elegant (and less high) case.

The construction is very ETA, and ETA will of course have played a huge part in developing this movement, as it’s a long time since Omega had an in-house movement.


I finally got the tool to adjust the beat rate, it’s an Omega original tool, and I paid ¬£301 for it. Believe it or not, it doesn’t fit properly, and only slides about 1/3 over the adjustment screws. Well done, Omega.

I adjusted the watch last Thursday, and have worn it since. Today is Tuesday, and the watch is exactly 1 second slow, so -1s in 5 days. That’s pretty impressive, and we will see if it continues to perform that well.


69 thoughts on “Service: Omega Seamaster Professional Planet Ocean 168.1665 / calibre 8500

  1. Good afternoon, Christian.
    My name is Duc Trung, and I live in Northampton, by the way.
    I have purchased one Omega Seamaster Aqua Terra from last year and of course, it is using 8500 Movement. But it has one problem, that it could keep time exactly 60 hours, even it has been wearing every day. I have tried to wind for extra power, but probably it doesn’t work. I am so very disappointed with my Omega Watch.
    Thus, could you give me an advice what should I do with this issue. I really want to sell it or exchange to Rolex watch, even though I paid £4000 for that.

    • I don’t quite understand the problem. Is it that your watch only works when you manually wind it? In that case, e.g. that the autowinder doesn’t work, you probably just need a new reverser wheel. Omega should sort that out on warranty for you.

    • Hi Christian.
      I am so sorry, my stupid grammar. Basically, Omega 8500 movement power reserve is 60 hours. But my Omega watch could not keep 60 hours, just around 40 to 42 hours. I worry that my watch has a problem with its barrel. However, I do not keep the warranty card, it has been sending back to my country last month. How much does it cost for that service, and could you fix that?
      Thank you very much for your comment.
      Phan Tran Duc Trung

      • Hi Phan,

        My guess is that a service will sort out the problem, but we should fit new mainsprings, and I can’t get those, as Omega doesn’t sell their parts to independent watchmakers any more. I’m afraid you will have to go to Omega with your watch.

        Best regards,


  2. Great analysis of the movement!

    Personally I think that the fingerprint and the dry residue around the barrel is a give away that an amateur has opened the case already, the airtight case obviously has been exposed to adverse atmospheric conditions. The high tech lubrication that has been scientifically developed in recent years surely can only be effective in a specific atmosphere i.e. a hermetically sealed enclosure.

    My 8500 has always run at -1 second per day in all conditions, this also leads me to believe that your case has been exposed to moisture which in turn has solidified the barrel lube / breaking grease.

    Looking forward to your next movement overhaul, totally love your blog!

    PS.. The date mech and keyless work has ETA written all over it!

  3. Hi. That’s a good article, well done. I have recently got an Aqua Terra model Can you advise me on one thing – when you adjust hours in “jumping” mode, your minutes hand keeps on working. Does it mean that if it takes me some time to adjust the hours or date (for example 15 times 1 minute over a month or two assuming I travel a lot between time zones), then eventually the hour hand becomes unsynchronized and lags behind minutes? Showing for example half past five when minutes hand is already at 45 minutes? I appreciate your comments. Cheers

      • Christian. Thanks for reply. Yes, the hour hand has 12 fixed positions. If it was 5:10 when I’ve pulled the crown to timezone position, then it would have 5:10, 6:10, 7:10 and so on positions. But what happens if I screw the crown back after 10 minutes of adjustments? Is the hour hand going to show 5:10 or 5:20?

  4. Good thoughts and review, though I wish people would stop putting Rolex on this mile high pedestal.

    I totally get that Rolex have their movements licked, but as such charge a lot more for their watches. However I really dislike the look of them all apart from the New 2016 Explorer and Air King. But they retail at over £4K and so no matter how much better they are I wont be buying one yet and certainly not for my 1st luxury watch.

    Rolex are king as they have been perfecting their watches for decades (and dont have too many iterations like Omega) and dont care for “marketing decisions”, but if someone doesn’t like them, I really don’t care that they are slightly better. I’m not buying one because it’s a better watch and not like it. Would I prefer Omega to be never associated with Swatch and ETA, yes of course, but I’m happy with (soon to be) my PO 45.5mm.

  5. Hi Christian,

    Thank you so much for all the info, experience and knowledge shared with us. It was very useful for me.

  6. Hi Christian
    Greetings from Australia .Great review of the Omega 8500 movement, good to have a pro like yourself give a review on watches. I would like your advise on a Omega Seamaster 300 Master Coaxial I purchased on 14/12/2015. By the way Watch Time magazine did a review on this watch and said it was one of the most accurate watches it ever tested. My watch ran at a brilliant -1 seconds a day up until mid June 2016 and then it went funny gaining time every day and as of yesterday it was + 5.1 s a day. Very disappointed only had the watch 7 months and now in for a service to regulate it. Of course Omega Service tried to convince me that it was adjusting to the way I wear it. What a load of bull—-t. For 6 months it ran at -1 s a day and suddenly started gaining time. I always take good care of my watches , wear them all day and never wear them while doing active physical work. Could you please give me your take on my dilemma. Is it just bad luck my watch timekeeping became irregular(poor QC before leaving the factory) or is it something more to do with a flaw in this 8400 movement.
    Many thanks in anticipation of your reply.

    • Hi George,

      I only had the one watch, so it’s hard to make a good conclusion from that. It looks to me like the co-axial escapement used by Omega has a problem with service intervals / timekeeping. They are great when they are freshly serviced, but loose accuracy very quickly.
      I remember a conversation I had last year in Biel at Omega, talking to a guy who was pretty high up on the ladder. We talked about the co-axial escapement, and I questioned its merits in terms of service intervals. The guy turned to me and said “Mr. Dannemann, you have to understand, this was a marketing decision.”. He didn’t say any more about the co-axial escapement, but I think I understood his comment.
      The watch I wear most is a Rolex with a 3135 movement, and I don’t have a watch with a co-axial escapement in my collection.

      Best regards,


  7. The service cycle for the Omega 8500 with silicon balance spring is set on a generous 6-8 year according to Omega, it only depence on the conditions how it is used.

  8. I see Omega fans are still taking it personally!

    Yes, the watch was already old when it was bought, but it’s not that old, and wasn’t worn for its first years. Modern oils and dirt should not have accumulated in that time. So it looks like their movements ain’t all that after all. Although when they are cleaned and tuned properly, they are very good performers – as they should be, with all that ETA knowledge behind them.

  9. Hi, that’s a great and detailed review!! I have one very similar to yours and was wondering if you know the crown reference. I need to change the crown, mine has a 2500 cal PO crown in it, I bought it used and certified, however I did not pay attention at all and now I want to make it 100% original.
    I cannot find any reference of anything to get the original crown for this PO.
    Hope you can help me!

  10. I’ve made a quick calculation, and in my estimation your watch is a bit older than five years (could be purchased one and a half year ago though). Is it odd that a 5 year old watch need to be serviced even if it was not used during the whole time?

  11. “So no chance of ever fitting this into a more elegant watch, which is a shame.”
    Guess what: in 2015 Omega came with a modell named Globemaster. Its diameter is 39 mm and the thickness is 12 mm. So much for your insight… ūüôā
    And suggesting that 8500 movements need to be serviced in every one and a half year is nothing but hostility. Movements can fail. I bet 3135s break down once in a while. And maybe you should consider that your watch is not 1 and half year old. I mean look at the serial number. It starts with 85. I bought my PO in December 2013 and the serial number starts with 88. This is pretty big of a difference.

    • I have a very small wrist, and 39mm is way too big for me. It’s a matter of your point of view, but from mine, 39mm isn’t elegant. My fault for my small wrist I guess.
      There was no suggestion that the movement needs a service that often, it’s just that this one needed a service. Quite possible that it’s been lying around at the dealership for quite a while.
      No need to get upset here.

      • Okay, maybe it’s not elegant, but it’s more elegant than the PO, isn’t it? ūüôā There is a smaller version of 8500, called 8520 which is fitted in the 37.5 mm POs and other ladies watches. It comes only with one barrel but beyond that it’s pretty much the same as the 8500. And its rotor has ball bearings! Anyway, the 3135 has got similar dimensions as the 8500. They’re big but they’re robust. ūüôā

  12. Thanks Christian, I have never seen this servicing before and it was nice to have a look inside this watch, I have learned and seen much interesting things this way. I do hope indeed that all the specs Omega stand for do come true and not that my Omega De Ville 8500 (Si14) does have the need for a service within a few years. Mine watch does have an average of -1 sec/week on the wrist, but with resting for the night with the crown up. The magnetism resistance for this type of watch is not official known, but it would not surprise me if it has a value of 1000 Gauss, I hope we ever will know.

    Kind regards,

    • Hi Arno,

      As long as the accuracy is fine, you won’t need a service. In theory, you should get 5 to 10 years out of your watch without it needing a service, but this movement is relatively new, so we don’t have that much experience with the service interval yet.

      Best regards,


  13. Hi I just purchased a 2 year old po 8500,after reading your review,I was surprised to learn about the service interval,I only plan on wearing it on special occasions,would that have an effect on the service interval, and how much is an average service,and also how can I contact regarding your location, I also have a 2008 seamaster professional chronograph,that will be in need of a service, regards butler95.

    • Hi Carl,

      The service interval should be 5 years or so, and you will pay around £160 with an independent (plus parts), and quite a lot more with an accredited repairer. Please have a look at our booking page regarding your chronograph.

      Best regards,


  14. Just a quick reply. I think the watch that you serviced has a flaw in the DLC coating for the barrels. It’s well documented in the forums and it would be advised that the owner gets his watch checked into Swatch Group for a free replacement on the barrel part.

  15. Hi Christian,
    It might be still too new, but what would be your expectations re cal 9300, having dealt with 8500?


  16. I own and collect mainly modern Rolex and Omega. I have an Omega AT 8500 and its accuracy is astonishing. It’s running at +1 at all positions.

    I would agree that in terms of finishing, modern ceramic Rolexes like the Sub C is better finished than a PO8500. But the longer power reserve of the 8500 is a god send. I can put the watch away on Friday evening and when I take it out on Monday morning, it will still be running.

    No doubt I love my DJ and Sub C the most but my AT, SM 300 and Speedy Pro ranks among my top 10 watches and the most heavily worn.

  17. Hello. What have i seen is, the failure reports of cal. 8500 are extremely rare. I have also seen a lot of watches with cal. 8500, working perfectly and accurate after a 4-5 year without any service.

  18. Thank you for an excellent informative blog. I have a PO 42mm Ti with the new 8500 movement with the S14. My power reserve is also very good lasting well into 52-56hrs. As for accuracy I find it excellent I last set it on 1st October cause September only has 30 days. I’ve just checked iPhone (not very scientific) but check it this way since I’ve had the watch and its gained 4 seconds. I do wear the watch a lot and I’m not sure but I think it helps with keeping time. I hope it doesn’t need servicing for a good few years. I only bought it new in May 2015 so budgeting for 2020 !!!

    • Hi Sean,

      give the WatchCheck application for your phone a try. It syncs inmediately with an NTP server or GPS (if you are out of net), then you can take the comparative measure from your watch. It fills a log for as many watches you have and let your know the deviations and averages. Very nice and handy, indeed.
      Best regards.


  19. We were told by Omega that the co-axial super in accuracy and less service is required … well.. thanks WatchGuy to show us the other side of the coin..

  20. The thing is that i¬īve owned a 2500c based Coaxial Planet ocean

    I remember there was no way to get it under +5 seconds a day (had it serviced and adjusted).

    I also remember that the 2500A and 2500B were 28,800BPH and they had to reduce it to 25,200 becuase the mainspring didnt have enough torque to move the watch and it would stop when placed crown up and the seconds hand would be around the 40-50 second area.

    I think thats also the reason why the 8500 has a double barrel, it needs the extra torque to operate correctly. which makes me wonder why they kept it at 25.200 if the corrected the power issue.

    I just feel like the 8500 is a product of turning all the patches applied to the 2500 over its life to official features, things that were implemented to correct errors suddenly become features of ruboustness…

    • Still not sure exactly what was wrong with the cal 1120 used in the seamaster 300M. Mine keeps great time, and allows for quite a thinish watch. And, I think the 2500 was only a modified 1120 with the co-axial bit. But maybe, who’s going to buy a new Planet Ocean if it has the same old cal as their 300m.

      • I guess they wanted something unique and launch their new diver with their new “in house” coaxial movement,

        unfortunatly the 2500A and 2500B were hack jobs and the C and D varities were patchwork.

      • The 2500 is a modification of the ETA 2892.

        And in my opinion this 8500 is a generic ETA movement and no Omega in house movement. The 1120 may be the last real in house movement ever made by Omega als long as it belongs to Swatch Group.

        • I think its the other way around, the 1120 was a off the shelf top grade 2892,

          the 2500 was a 2892 modified to carry a coaxial escapement, badly modified, it was a mechanical test bed which should have never been released to the public, but they needed it for the planet ocean,

          the 8500 is a new movement developed by ETA and Omega, but thats to be expected since ETA is the movement manufacture for the swatch group, except for custom made limited run movements, ETA makes all the movements, some movements are brand specific, the PowerMatic 80 for tissot, the sistem 51 for swatch, the H20,H21 and H31 for Hamilton, the 8400, 8500 and 9300 coaxials for omega.

          A curious detail, that new shock absorber with the T vs T shape is called NivaShoc, the curious thing is that they were also present in the first runs of the hamilton H31 and H21 7750 modified movements,

    • The mainspring of the 2500 series movements has alot of torque; the reason for reducing the speed of the balance to the somewhat unique 25200 vph has nothing to do with this, but the fact the co-axial escapement performs better at 25200 vph. When it comes to chronograph co-ax movements, Omega keeps them running at 28800 vph – it helps measuring parts of a second with a second hand moving eight times for every second.

      The reason Omega decided to opt for twin barrels is that you get a smooth torque curve, without spikes, helping the balance to keep excellent accuracy also when the energy reserve is close to zero.

  21. as always a delight to the eye Christian, that one is a very beautiful watch and impressive movment, I was so impressed this movement has no quick date change mechanism!!! I’m used on going all the way the 24hrs or back and forth between 9-12 to change the date on my $70 Vostok watches… but never expected that on this expensive movement!

    • Umm.. I don’t think you get it. Your Vostok does not have quick set date nor an independent hour hand than can unhinge and move freely while the minute hand stays put.

      The Omega 8500 has an independent hour hand which is found on true GMT watches. This method is way more complicated to implement than a quick set date. Sorry but I don’t think $70 will cover a movement as complicated as this.

  22. Interesting. I seem to remember you analysed the co-axial movement a while back and concluded along the same lines – that in theory it was all well and good but in practice, the extra accuracy wasn’t there.

    And now it seems the long service interval isn’t there either.

    I can’t help but think this co-axial escapement is a bit of a gimmick, or at least a solution to a non existant problem.

    • Funnily enough, I was discussing the co-axial escapement with a colleague of mine today, and also said that it was the solution to a non-existing problem ūüėČ
      It’s the balance.

    • I also think it’s a gimmick, one that enabled Omega to increase prices and directly compete with Rolex. I also don’t understand the obsession with in-house movements. Limited-production high-performance car makers turn to big manufacturers for the drivetrain for a reason (like Pagani with AMG engines and Ferrari with Getrag gear boxes), so why not get your movement from a company that knows what they’re doing?

  23. Wow. And this Omega needed a service after only 1.5 years? I thought one ( and maybe the only) advantage of co-axial was the increased service intervals?
    Think I’ll keep hold of my Cal 1120 seamaster thanks. That keeps good time, and gets a service every 7 years (so far), i.e twice in the 15 years of ownership.

    • I have yet to see a co-axial movement that reaches the service interval of a nice Rolex 1670 or a 3135. Or the ETA 2892-A2 for that matter.
      The promise is there, and in theory, it should last a lot longer without a service, but in practice, I haven’t seen that yet.

      • Thank goodness for that, as I have just purchased (at a very good price) a new/non worn Rolex Sea Dweller with the cal 3135 over the Omega PO GMT. (preferred the 43mm size of the GMT).

      • Perhaps the first owner of your Omega liked to work with his hands out in the field or under the hood (bonnet?) of a sports car. I’ve learned the hard way that many of these Swiss watches are marketed with a tough, macho image but really need to live indoors. The salesman doesn’t tell you, but later the watch repairer does.

  24. Fascinating stuff though your piece has created a dilemma for me. I have been saving hard to buy one of these but I’m pretty concerned that a watch at that price point needed a service in 1.5 years. Do you think this is typical or that you were unlucky?

  25. I really enjoyed this post. I have bought a used PO GMT (same orange and black dial) a little more than a week ago. It is now exactly one year and ten days old. I set it on the day I got it and it has been dead accurate so far: +/- 0.0s in nine days. So it seems that it is quite possible to get a very well adjusted Omega, and it seems you could get a slightly worse one. It is perhaps not a movement but more a QC issue of your particular watch? I mean the fingerprints on the back of the dial and spots of dirt, etc, might point that way.

    I just know that by tomorrow something will break, now that I am bragging about the accuracy of my PO :).

    I really hope you will get the adjustment tool, so that I can send you my watch once it needs servicing (of course depending on your availability).

    I read the post about swatch group anti-competitive practices but I am hoping that as long as nothing really fails mechanically, my Omega can still be serviced by you? I noticed that you can still source the mainspring as it is manufactured outside the Swatch group and as long as I take care of my watch and not subject it to a pneumatic hammer, that is all you would need for a regular service, right?

    Sorry for a long post.

  26. So, the 8500 movement is not a pure “In-House” movement of Omega, but an ETA movement?
    Which movements do they actually make?
    I just wonder why should I pay for a watch (which i considered buying) that
    does not have an In-House movement…

    • The movement was developed during 2000-2007 with Omega in co-operation with ETA, Nivarox FAR and Piguet – i.e with the very best of know-how within the Swatch Group. You can read all about the development of this masterful movement in the 2007 october-issue of Watch Time.

  27. I’ve been waiting for this type of interesting information on these movements, thanks! I’m still unsure of the real world benefits of these inovations because my Nomos Club Automat with standard swiss escapement is extremely well regulated in various positions and I certainly hope it won’t need a service after only 1,5 years! What are your thoughts on long term issues: do you think this was a fluke or can owners expect to have to service these watches more frequently?

  28. Hello Christian,

    “The movement is slightly slow, but I can‚Äôt get hold of the special tool to adjust the balance.”

    Will you re-adjust it when that tool come to you, and let us know about the outcome?
    Thank you, best regards.


  29. “I should get it within the next two weeks for a mere ¬£300”

    …outrageous…just another example of the arrogant attitude of Swatch. Such costs will of course ultimately be passed to the watch owner. Another reason to boycott Swatch products.

    Very pretty movement with neat advances in watch movement tech but ultimately no better.

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