Maintenance on Electric Fins stabilizers

[Mambo42]

I think by now everyone knows I have electric fin, zero speeds stabilisation, on my boat. They are CMC stab 25 fins, which provide stabilisation underway, at anchor and on the dock. These fins are designed to break off if you hit a log or some other obstruction in the water, meaning you won't rip out the electric motors. The fins will float to the surface, you can pick them up, call the factory and they will come to either repair them or you get a new one. I have seen a super yacht in Turkey which had lost a fin, recovered it and 4 days later it was repaired and back on the yacht.

Many times people ask: 'what do you need in maintenance ?'
Luckily I can say that you don't need a lot of maintenance and so far I did not have any failures or problems with the system. I basically have them on 24 hrs per day, so am putting a lot of hours on the clock and that means I will need maintenance every single year. Maintenance schedules are every 2 years or 5000 hrs. The first 5000 hrs maintenance is replacing the seals on each motor. Those seals keep the water from coming into the boat, so have nothing to do with the electric motors itself.
Since I still had warranty I had this maintenance done by an official dealer of CMC, but this was not without surprises.
Last winter (2024 - 2025) my boat was in Italy and I thought that would make it possible for CMC to do the maintenance themselves. How wrong could I be !!
The official quote of the factory was beyond absurd, 15.000 euro for a 1 day job. Exchanging the seals themselves was 6500 euro, everthing else was travel, luxury hotels and luxury dinners for the workers. Needless to say I never reacted to this 'offer'.
Next came a company from Croatia, they wanted 6000 euro for a day's work, so they were also out of the window.
And then came another company from Croatia, they asked a more realistic 1600 euro for the work plus parts. The parts were 1400 euro (4 seals and 16 bolts), work was with 4 guys. They started at 9 in the morning and by 3 in the afternoon they were finished. So the total of the maintenance was 3000 euro plus VAT.

Process is as follows:
- removal of 8 bolts holding each fin to the motor
- removal of each fin (about 90 lbs each)
- cleaning of the outer ring which hides the seals
- removal of the 8 bolts (on each motor) that hold the seal cover plate
- removing the seal cover plate
- drilling a hole and screwing in a screw to pull out each fin
- cleaning the space where the new seals need to be installed
- greasing of each seal (2 per motor) and installing them
- installing the seal cover plate
- applying sikaflex 291i to create a seal between the seal cover plate and outer ring
- re-installing the fins (with 8 new bolts)

All the parts were cleaned before re-installing them.

After the boat went back into the water both motors were checked for leakages, none occurred. Stabilisers have been working fin without a problem. This maintenance happened in mid-May this year. My boat will come out in January again for some maintenance on the cutlass bearings and PSS seals, so I will do the 10.000 hour service at the same time. This is the service where the motors need to be opened up to exchange the grease inside the motors and at the same time change the seals again.
Since this is still part of the warranty I will have a CMC dealer do this service, after that I will start doing it all myself. Since we use our boat and stabilisers for more than 5000 hours each year it means I will need to do this maintenance each year.

 

[Mambo42]

Here are the remaining pictures

 

[READY]

Thanks for the detailed post. Reconfirms my decision to forgo stabilization on my Hatteras 48LRC as it is rarely needed and the cost plus maintenance is not worth it (for me) based upon how I use the boat.

 

[mvweebles]

Would never have occured to me to ask about maintenance requirements of electric vs hydraulic fins. At-rest stabilization has to be nice thought.

Thanks for the post @Mambo42

Peter

 

[Mambo42]

Would never have occured to me to ask about maintenance requirements of electric vs hydraulic fins. At-rest stabilization has to be nice thought.

Thanks for the post @Mambo42

Peter

My boat did not have any stabilisation and since I was going to install it any way I thought I may as well go for zero speed and that was the best choice I could make.
It is great to have a boat which is always stabilised.

 

[DDW]

The capital cost of all of the active stabilizers seems to be only the anti up. A bit like the razor vs. the blades. I remember reading about the development of the B777 and the bidding for the engine business between Rolls and Pratt. The airline buyer gets to specify. Engine salesmen were willing to give away the engines, because the service on them was so lucrative.

 

[Marco Flamingo]

Makes me wonder if I'm going to have any ongoing maintenance for my new anti-roll tank. It will be a year when we return to the US this spring. Installation cost was $400 total, as there was no haulout involved. It has worked continuously (+8,000 hours) since installation (works at anchor). Emptying and changing the liquid will take 30 minutes and cost less than $50, if needed. Maintenance can be performed anywhere. I'll post pictures if maintenance is required.

 

[Mambo42]

The capital cost of all of the active stabilizers seems to be only the anti up. A bit like the razor vs. the blades. I remember reading about the development of the B777 and the bidding for the engine business between Rolls and Pratt. The airline buyer gets to specify. Engine salesmen were willing to give away the engines, because the service on them was so lucrative.

Indeed many times people forget the maintenance cost for certain systems. As soon as seakeeper told me the bearings needed to be changed after 5000 hours and, in order to be able to do that, the whole system needed to be taken apart, I realised I would be in for massive cost. So for that reason (and the operating cost) I opted out of a gyro.
Same was for the operating cost of a pneumatic system, where a 4 Kw (220 V) compressor would need to run all the time.
I think the only system without maintenance is the new magnus rotor for zero speed. But the cost of a new one is about 140.000 euro.

With my system I was just appalled that the company itself wanted to charge me 15.000 euro for a 1 day job. Luckily I was able to find a company that did it for an acceptable price. After I saw how the guys did it I decided that as soon as the warranty will be over, I will start doing it myself. It may take me a day longer, but it will save a lot of money. The only thing I cannot get around is buying the seals and bolts, they will always be expensive.

 

[Pascall]

Indeed many times people forget the maintenance cost for certain systems. As soon as seakeeper told me the bearings needed to be changed after 5000 hours and, in order to be able to do that, the whole system needed to be taken apart, I realised I would be in for massive cost. So for that reason (and the operating cost) I opted out of a gyro.
Same was for the operating cost of a pneumatic system, where a 4 Kw (220 V) compressor would need to run all the time.
I think the only system without maintenance is the new magnus rotor for zero speed. But the cost of a new one is about 140.000 euro.

With my system I was just appalled that the company itself wanted to charge me 15.000 euro for a 1 day job. Luckily I was able to find a company that did it for an acceptable price. After I saw how the guys did it I decided that as soon as the warranty will be over, I will start doing it myself. It may take me a day longer, but it will save a lot of money. The only thing I cannot get around is buying the seals and bolts, they will always be expensive.

140,000 euros. Friends of ours had two installed two years ago for half that amount.

Kind regards,

Pascal.

 

[Mambo42]

140,000 euros. Friends of ours had two installed two years ago for half that amount.

Kind regards,

Pascal.

That might be the original Magnus Rotor, the one that gives stabilisation for under way. The new one, think it is called 'All in one'. is a bit more expensive. I got a quote for 130.000 and that was indeed for two of them, excluding installation.
Good part of the all in one system is that it won't need any maintenance and has a 5 year warranty.
I saw the new All in one on Boot Dusseldorf last year and it would be high on my list if we buy a new boat (if I can find it) which would need stabilisation. Not having to search for maintenance is a big plus.

 

[Pascall]

All in one, I watched the promotional video.
500-kilogram units at the rear of the boat, that's a lot of weight so far back.
These protrude about a meter sideways when in operation, which your neighbors in the marina won't like.

Mvg,

Pascal.

 

[Mambo42]

All in one, I watched the promotional video.
500-kilogram units at the rear of the boat, that's a lot of weight so far back.
These protrude about a meter sideways when in operation, which your neighbors in the marina won't like.

Mvg,

Pascal.

It is a lot of weight, is not for every boat, that is for sure.
As for being in the marina with them. Here in the Med you will have that space in a marina, but indeed in ports in the high season that might be a different situation.
I don't know if DMS also has a dock mode, like I have on my fins. In dock mode my fins are limited to 20 degrees max from center, instead of 40 degrees max when underway. That way the fins never stick out of the side of the boat, so I can actually use them when I am next to a pier.

 

[guy with a boat]

…
Good part of the all in one system is that it won't need any maintenance and has a 5 year warranty.
…

They need no maintenance or the manufacturer has no maintenance schedule? They’ve really got something if they can build a machine with any moving parts that can run for 5,000hrs/year indefinitely without any service. That may be a first.

 

[Mambo42]

They need no maintenance or the manufacturer has no maintenance schedule? They’ve really got something if they can build a machine with any moving parts that can run for 5,000hrs/year indefinitely without any service. That may be a first.

When I was at Boot Dusseldorf I was told that maintenance was near zero, no changing of seals or bearing. Perhaps some grease will be necessary, but I guess not a lot more. Compared to other (hydraulic, pneumatic, gyros and even my fins) that is pretty good.
I checked the brochure (see pdf) again and you are right, it says minimal maintenance.

 

[DDW]

The rotor systems have gear boxes, drives, and a large swinging seal, so hard to see why the maintenance would be so much less, it is similar mechanically to fins. Gyros seem like the worst case for maintenance. I found my rolling chocks to be nearly maintenance free - they only required extra antifouling.

 

[Mac2]

How much power are you using? Would you compare it to running a refrigerator 24/7?

 

[Gypsy Island]

When I was at Boot Dusseldorf I was told that maintenance was near zero, no changing of seals or bearing. Perhaps some grease will be necessary, but I guess not a lot more. Compared to other (hydraulic, pneumatic, gyros and even my fins) that is pretty good.
I checked the brochure (see pdf) again and you are right, it says minimal maintenance.

Forget about that, not only the seal will wear out after a few thousand hours, even more concerning is the growth near the seal, especially barnacles which will most likely damage the seal.

Back in 1988 NAIAD stated the seals should only be replaced every 4000 hours without any timely limit.

Now they recommend replacing the 2 stacked seals every 2 years and more frequently if the stabilizers are rarely used.

My NAIADS were at least 20 years without service and when i tried to remove the seals, they were so brittle, they literally fell out in pieces.

 

[Mambo42]

How much power are you using? Would you compare it to running a refrigerator 24/7?

Electric fins only use power when they are actually operating. The control boxes use next to nothing (which is DC) and the fins use when they are stabilising the boat. Depending on the severity of the disturbance they will use more or less. If it is a gentle disturbance they may use 50 - 100 W (at 220 V), but if it is a heavy disturbance they may use 500 - 600 W for a moment, then slowly die down again to nothing. Sometimes they simply gently move back and forth all the time, other times, like e.g. now, they are most of the time not moving at all.
In general I get to about 10 - 15 amps per hour (at 24 V) while on anchor. Underway it is much less because they are more effective while the boat is moving, they need to work less. Obviously, if we end up in an anchorage which is pretty rough they will work more, but they will always keep up stable, even if we are in heavy TS.

 

[Mambo42]

Forget about that, not only the seal will wear out after a few thousand hours, even more concerning is the growth near the seal, especially barnacles which will most likely damage the seal.

Back in 1988 NAIAD stated the seals should only be replaced every 4000 hours without any timely limit.

Now they recommend replacing the 2 stacked seals every 2 years and more frequently if the stabilizers are rarely used.

My NAIADS were at least 20 years without service and when i tried to remove the seals, the were so brittle, they literally fell out in pieces.

There is a cover plate completely covering the seals, so no barnicles can grow there.
I have no doubt the seals will last more than 5000 hours, but since I am still under warranty I am just abiding by the prescribed schedule. Last service I took a look at the seals when they came out and they still looked OK. The outer seal was obviously in a much worse condition than the inner seal, but if I would have to judge I think they would have been able to continue for quite a few more years.
And these seals are the seals that have to keep the water out of the boat, so even if water would pass through the motors would not get damaged at all, I would just get water in the boat.

 

[Mac2]

Learning a lot here. I’m wondering why I haven’t heard more about electric fins. Not sure you know the answer, but do the fins need to be larger for at rest stabilization?

 

[Mambo42]

Learning a lot here. I’m wondering why I haven’t heard more about electric fins. Not sure you know the answer, but do the fins need to be larger for at rest stabilization?

That is what I thought as well, but I was told that because they are electric it is not necessary. Electric motors can create a lot of torque, much more than hydraulic actuators ever will. For that reason they can move the fins much quicker and with much more force than a hydraulic actuator, thus keeping the boat stable on anchor.
Electric fins, for some reason, are still not very known, which does surprise me. When I started researching stabilisation I looked at every possibille technique and in the end I decided to go for electric fins. I thought it was brand new, but it has been in use since 2008 already. However I do think that the LiFePO4 batteries, and modern inverters have made electric fins more popular the last couple of years.
I could run my fins off my AGM batteries, but I could not run all other equipment at the same time. So I still needed the generator to run the stabilisers plus the dishwasher, induction cooking plate, washing machine, airco etc at the same time. Now that I have LiFePO4 I don't need the generator anymore, I can run my stabilisers and other equipment without a problem at the same time.

I did notice that the marketing department of CMC is about as bad as it can get. I actually have the idea they really don't care about boats in this size and that is weird since they do make stabilisers for them. Apparently they have been focussing on the larger yacht market, but even there they do a horrible job. As long as hydraulic stabiliser fins are able to secure contracts with manufacturers of boats, CMC is doing a bad job. And that is weird, because having these electric zero speed fins now for a little over 2 years, I cannot even imagine ever going back to only underway stabilisation.
Soon we will have the largest Boot show in Europe, called BOOT Dusseldorf and I am sure all the stabiliser producers are there, but CMC has never been there. I have no idea if they show up on Trawlerfest or at the FLL boat show or the Miami boat show, but what I do know is that if you keep your product a secret...........you are not going to sell a lot and CMC is the company that invented the electric fins.

 

[Mac2]

Great explanation. The torque of electric cars really confirms what you are saying. You are probably CMCs best commercial. Keep us posted on their performance.

 

[twistedtree]

I honestly don’t understand the torque comment. A suitable hydraulic ram and lever arm can create pretty much any torque you want. Same with a hydraulic motor. As a counter example, many windlesses are available in electric and hydraulic versions, and the hydraulic versions invariably have more lifting power, ie torque at the chain wheel.

 

[Mac2]

I honestly don’t understand the torque comment. A suitable hydraulic ram and lever arm can create pretty much any torque you want. Same with a hydraulic motor. As a counter example, many windlesses are available in electric and hydraulic versions, and the hydraulic versions invariably have more lifting power, ie torque at the chain wheel.

Maybe “quickness” would be a better term? Are there hydraulic fins that can be used for at rest stabilization?

 

[twistedtree]

Maybe “quickness” would be a better term? Are there hydraulic fins that can be used for at rest stabilization?

Yes, mine can do at rest.

 

[twistedtree]

I don’t mean to imply that electric actuators aren’t up to the job or are inherently inferior. By I am saying that I don’t think they are inherently faster or more powerful than hydraulics

 

[KnotYet]

Hydraulic power is just energy conversion. My hydraulic fins are powered by the port engine.
They could be powered by an electric pump just as easily, though.
Electric fins are relatively new in smaller boats. They will probably dominate as more boats
are built with greater electrical capacity and the cost of the electric actuators comes down.

 

[DDW]

One thing electric actuators don't do is leak hydraulic fluid. Of course they can leak electricity but I'd rather clean up electrons than hydraulic fluid. I own power boats, sailboats, tractors, back hoes, man lifts, forklifts and jacks. Every one of them has hydraulics and leaks hydraulic fluid, now, in the past, or will in the near future. So if I were to consider stabilizers, I would absolutely be looking at electric.

 

[klee wyck]

I don’t mean to imply that electric actuators aren’t up to the job or are inherently inferior. By I am saying that I don’t think they are inherently faster or more powerful than hydraulics

It is the compressibility of a fluid medium that creates the lag versus the instantaneous change of direction in electric direct driven fins or rotors. It seems like nothing, but isn’t.
The phenomenon is more apparent in rotors because you do not wait for the change in defection to go from positive to negative as the forces on the vessel change. just and instantaneous change in direction of rotation.
I currently own neither.

 

[KnotYet]

One thing electric actuators don't do is leak hydraulic fluid. Of course they can leak electricity but I'd rather clean up electrons than hydraulic fluid. I own power boats, sailboats, tractors, back hoes, man lifts, forklifts and jacks. Every one of them has hydraulics and leaks hydraulic fluid, now, in the past, or will in the near future. So if I were to consider stabilizers, I would absolutely be looking at electric

Every element in a system has inherent weaknesses but fluid leaks aren't really inherent, IMO.
The 25 year old stabilizer system in my boat has had no leaks that are apparent to me yet.
Granted I have only owned it for 4 months but there isn't any staining or accumulation of oil
where it shouldn't be.
How about steering? It seems most trawlers have hydraulic steering. Some steering systems develop leaks but it isn't an inherent problem to be corrected, IMO. I think that the biggest
advantage of electric stabilizers is the reduced parts count and thus improved reliability.

As I said above, electric stabilizer systems will probably dominate future builds just like
electric cars will probably dominate future transportation systems.