# Marine Air Conditioning Install



## CaptTony (May 22, 2011)

I'm currently shopping for a new-to-me boat in the 37' range (give or take a few feet). This being Florida where it's 90 degrees or more every day in the summer, I'm considering air conditioning at the dock (no generators). 

Some boats at which I'm looking have air and some don't. What would it take cost wise and labor wise to install a marine system? I did a search of the forums and all I have come up with are threads about home window units and RV air conditioners. I would want a true marine system.

Thanks for any info.


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## deniseO30 (Nov 27, 2006)

"True marine usually means 2 things. water cooled and price. Most are DIY friendly. Unless you want to go with built up systems and multiple air handlers.


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## Sabreman (Sep 23, 2006)

There are a lot of steps involved and while each isn't especially difficult, they are time consuming. You would have to install a through hull and seacock for the cooling water, pump, condenser, ducting, 120VAC, thermostat, condensation drain to the bilge, and another exit above the waterline for the water outlet. Figure about 20 hours at $90-$100/hr yard rate. Figure about $1500-$2000 for the unit itself. So I'd ballpark it at between $3000-$4000.

Suggestion: buy a boat with a non working unit and replace it. All the infrastructure will be in place (ducting, through hull, AC, etc) and you may be able to just drop in a new unit. Ask for $4000 off the purchase price and do it yourself for $1500-$2000 and about 10 hours.


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## CaptTony (May 22, 2011)

Thanks for the replies. I'm looking at several boats, but one in particular is way below the market for what it has. Adding an air conditioner would not even bring it close to what others are asking for the same or similar boat. 

Anyway no decision yet and your information gives me a better idea at the final cost if I choose to add an air conditioner on a boat that doesn't have one.


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## Alive3and3Well (Aug 16, 2010)

Remember, also the marine air conditioners have a somewhat high electric current draw. Keep that in mind with size of breakers, wire gauge, etc. A 10,000 btu turbo would draw close to seven amps.

I bought my current boat in the summer in Florida. My 33' foot boat has fore and aft marine a/c compressors and still fought to keep up in brutal Florida heat. (Each was 7,000 btu)


Good luck in buying your boat!


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## chuck53 (Oct 13, 2009)

I've got a Catalina 34 that I put a 16k BTU AC unit in when I bought the boat 4 years ago. I believe the unit was about $2400 and $900 for the install which we were able to do on the cheap. I had an unused thru hull that we were able to use for the cooling water which means we didn't have to haul the boat and install one. We also didn't run any duct work...just one large output vent in the center of the boat. I'm guessing those 2 things saved me at least $7-800, maybe more.
Also the previous owner had already upgraded my 120v electrical panel to handle an AC unit.


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## captain conrad (May 18, 2006)

I have a portable unit I bought at home depot drain into the bilge 10,000 btu works fine.
I vent out of a dorad vent and secure it when I'm underway $300.00


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## j34035 (Nov 10, 2006)

I have installed 3 over the years. All 3 have been 16000 btu units. A couple of things I have learned: Dont scrimp on the pump. Get one that will pump plenty of water. Make sure you size your duct work and return air as per manufacturer's spec. If you make supply too small, you will restrict your airflow and the velocity will be high enough it will be loud. Make your return small, and it will choke your entire cooling capacity. Don't use the flex duct if you don't have to as the air flow loss is horrible with that stuff. I have used sewer and drain pvc pipe successfully in 2 installs. Stuff is cheap, thin, and easy to work with. Use duct tape to seal it and you have a system that can be taken apart as needed. Mount your water pump and piping so there are no air-locks or you will have a heck of time purging the air and making water flow. Centrifugal pumps dont like air, they just will not pump it. It is a lot of work, but so worth it when you are done. Good luck with your project.
DD


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## CaptTony (May 22, 2011)

Thanks, DD. You made some excellent technical points to remember.


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## Yorksailor (Oct 11, 2009)

I fitted two Marinaire 16,000 BTU units, the dealer is in Miami, and they have been used on an almost a daily basis for 18 months.

They are plug and play integrated units and even have built in gauges for refilling refrigerant. They do need a dedicated through-hull and a good sealed water pump which the dealer sells. The units come with plug and play thermostats with remote controls. We put one in the main cabin and one in the main bedroom and neither needs extensive ducting ducting. Although a better installation would have run ducting to the guest cabin which cools passively from the main cabin.

A helper and myself fitted both units in 2 days. We already had the through-hull and it was just a matter of building a frame in a closet to hold the units and running water pipes including a condensation drain and the A/C cables off the main control panel. Since we did not know enough about making the installation complicated we did it as simply as possible and they work great!

Two 16,000 BTU units are more than adequate for a 55 ft boat even thought we have been either in Miami or south of Miami in places like Panama.

Manufacturer of quality marine air conditioning units and self contained marine air conditioners - Home

Phil


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## Minnewaska (Feb 21, 2010)

I have found the biggest mistake made, when installing air conditioning, is either insufficient ducting size or multiple ducts of different sizes that become terribly imbalanced. Sometimes there is little choice, as there is little room. However, there is more to proper distribution than just routing whatever ducting fits. 

We have three units aboard. The one that works best has essentially no ducting. It blows from one vent above the air handler in the master stateroom. The other two will run multiple cabins. The salon has the largest ducting, where the units are located and they get smaller as they travel foreward into the staterooms. Technically, I think this should be the opposite. While the salon is easy to cool down, the forward staterooms are not. To get them too cool, you really need to refrigerate the salon. I suppose there are worse problems.


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## Seaduction (Oct 24, 2011)

I installed Mermaid Air conditioning (company is in Fort Myers, FL) myself on my IP 31 a few years ago, after moving to Florida. Their instructions are very good and installation is very DIY friendly. Their service is wonderful. If you call them you actually speak to a knowledgeable human. Just adhere to the instructions, and be cool.


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## Group9 (Oct 3, 2010)

captain conrad said:


> I have a portable unit I bought at home depot drain into the bilge 10,000 btu works fine.
> I vent out of a dorad vent and secure it when I'm underway $300.00


I thought about getting one of those for my boat. I have a small window unit that I place over a hatch with a custom cover I made from a storage bin. The good thing is I don't have to leave a seacock open, as my inboard AC requires.

The really sad thing, is that this $200 AC cools the boat really well, actually maybe even better than the quite expensive installed MarineAir system in the boat (which costs quite a bit more than $200).

Since I don't use the AC anywhere but at the dock, I think if my Marine Air ever goes out, I am not replacing it.


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## Jolly Roger (Oct 11, 2013)

I agree with everything others have said. I installed two 120 volt units in my Down East 45 shortly after I bought it three years ago. I haven't touched them since, and they are a life saver for us here in Titusville. I had never done this before and if you want to read how it was done go to my website. Schooner Britannia, a Brigantine Schooner being renovated.
One thing I would advise: get the outlets as high, and as straight as you can. Mine are ultra-efficient, being made of plywood and straight from the fans into all the cabins and heads. We have 75 degrees when it's 95 outside-_*and *_it works from our generator when at anchor.
It's not rocket science, just common sense really, and of course money and work.


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## svHyLyte (Nov 13, 2008)

Jolly Roger said:


> I agree with everything others have said. I installed two 120 volt units in my Down East 45 shortly after I bought it three years ago. I haven't touched them since, and they are a life saver for us here in Titusville. I had never done this before and if you want to read how it was done go to my website. Schooner Britannia, a Brigantine Schooner being renovated.
> One thing I would advise: get the outlets as high, and as straight as you can. Mine are ultra-efficient, being made of plywood and straight from the fans into all the cabins and heads. We have 75 degrees when it's 95 outside-_*and *_it works from our generator when at anchor.
> It's not rocket science, just common sense really, and of course money and work.


Nice web-site. Love the square sails!


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## Jiminri (Aug 26, 2012)

How loud are the marine a/c units?

I've considered having an a/c unit installed on my boat. My yard advises that the best location would be up high in the wet locker in the forward stateroom. It would need essentially no ducting in that location as it would cool the stateroom and blow straight back into the salon.

My concern is that it might be loud, being right next to the berth. Are some units quieter than others?


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## Minnewaska (Feb 21, 2010)

The combined units are a bit loud. They also make split units, where the only noise in your room is the air handler. However, even the air flow noise can be loud and, due to the poor insulation, cycles on and off frequently.


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## Jolly Roger (Oct 11, 2013)

Jiminri said:


> How loud are the marine a/c units?
> 
> I've considered having an a/c unit installed on my boat. My yard advises that the best location would be up high in the wet locker in the forward stateroom. It would need essentially no ducting in that location as it would cool the stateroom and blow straight back into the salon.
> 
> My concern is that it might be loud, being right next to the berth. Are some units quieter than others?


This is how mine are installed. I listened to some units before I decided, but I came to the conclusion they were all about as noisy as each other. My aft unit is in the master cabin and the forward unit in the foc'le. I reduced the compressor/fan noise considerably by using 1" thick foam all round. I also reduced the wind noise by building a V shaped baffle just before the outlets. 
Whatever the noise, it's till better than 100 degrees in the cabin at night in Florida.


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## Jolly Roger (Oct 11, 2013)

My boat had a Carrier RV external unit when I bought it, which aren't cheap either. The problem was it only blew cold air into the cabin where it was mounted above, and we had to transfer it to the aft cabin hatch at night, then back to the main hatch in the daytime. It was also as noisy as my installed units, but it couldn't be insulated, and needed about six fans to direct the air into other areas. An external unit, whether Carrier or window unit is okay for a small boat with say, only one cabin and saloon, but not if you want to direct air to other areas, like the heads. But then they are much cheaper than a purpose installed system.
Mine was expensive, but we prioritized it above nearly everything else, and are now as cool as any house. _And _we can get toasty warm in winter, without it being boiling hot in one cabin and cold in another.
I also think a neat installation is bound to add to the resale value, over a similar boat which doesn't have AC.


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## svHyLyte (Nov 13, 2008)

We have had a King Air 16,000 BTU unit installed in a nook under the settee return in the saloon on our boat since 1996. The original unit lasted 16 years and died in 2012 as, unbeknown to me, the fellow that did the original install didn't do the condensate drain properly and it would periodically wet the underside of the compressor which eventually rusted through. Considering its age, rather than simply replace the compressor, I decided to buy a whole new unit with electronic controls rather than analog as on the original. The unit is very efficient, easily run from our 4.2 KW generator, and very quiet with the fan speed varying up or down automatically depending upon how far the ambient temperature is from the set point on the electronic thermostat. Tho' centrally mounted, with a few small Hella fans to move air around, the unit keeps our entire boat very comfortable, even in the heat of the summer in Southwest Florida, and can keep the boat a cold as a meat locker if permitted to do so. Best of all, the service by the company has been exceptional.

A few tips: Most condensate pans are designed with only one drain outlet which only works properly if the drain is oriented fore-n-aft on or near the center line of the yacht. Our unit is mounted cross-wise and so was made with drain lines on either end of the pan and will so drain to the bilge regardless of what tack we take up as we leave an anchorage (for example). Secondly, ours came with a March MDX air-cooled raw water pump which is problem free and efficient. Some folks have fitted Cal pumps that have proven problematic as they were originally designed for submerged (and so water cooled) applications and are subject to failure due to differential expansion between the motor housing and the pump-chamber housing, causing leakage and early demise. (And they are costly to replace!). Lastly, it is wise to install the raw water lines with unions at convenient locations so one can easily disconnect the lines and thereby back-flush the cooling coils and, occasionally, recirculate a solution of RydLyme or a similar material to clear out deposits that may accumulate. (We do that as part of our annual maintenance regime.)

FWIW...


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## Minnewaska (Feb 21, 2010)

Since we're all tossing out as much info as possible, here's a few more ac tips. The raw water pump filters must be kept pretty clean. As the block with weeds or algae, the system becomes inefficient and then shuts down.

Secondly, the condensate pans rarely seem to fully evacuate. There is often a very slight amount of water that doesn't make it down a tube and can cause some mold. Drop a disinfectant tablet in there every few months.

Will probably think of more random marginally useful info.


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## PalmettoSailor (Mar 7, 2006)

Are there brands besides the Mermaid folks would highly recommend? 

The control unit on my AC/Reverse cycle heat unit was killed by lightning and rather than spend $800 on a repair, I was thinking to replace the unit as a DIY project since all the hard work (AC power, through hull, pump, ducting) is done. 

Since I wasn't able to get a repair estimate before the start of this season I decided to suck it up until the Annapolis boat show to see if I could get a deal.


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## Group9 (Oct 3, 2010)

Minnewaska said:


> Since we're all tossing out as much info as possible, here's a few more ac tips. The raw water pump filters must be kept pretty clean. As the block with weeds or algae, the system becomes inefficient and then shuts down.
> 
> Secondly, the condensate pans rarely seem to fully evacuate. There is often a very slight amount of water that doesn't make it down a tube and can cause some mold. Drop a disinfectant tablet in there every few months.
> 
> Will probably think of more random marginally useful info.


Another point to remember is that it will eventually become necessary to descale any air conditioning system that uses seawater for cooling to keep it running at max efficiency. The same as with engine cooling systems that use seawater for cooling.


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## svHyLyte (Nov 13, 2008)

Group9 said:


> Another point to remember is that it will eventually become necessary to descale any air conditioning system that uses seawater for cooling to keep it running at max efficiency. The same as with engine cooling systems that use seawater for cooling.


This is the reason that (in Post #20) I suggested the use of unions in the raw water feed and discharge lines (good quality hose connectors will work) that allow one to disconnect the lines and back flow a rinse through the system to clear sediment or recirculate a descaling agent such as RydLyme or Barnacle Buster and water through the unit periodically. We do so annually.

Regarding the use of a anti-bacterial cleaning agent in the condensate pan, one should not use any material that might promote corrosion such as a piece of a pool chlorine tablet that I have seen used by others. A squirt of a biodegradable bilge cleaner periodically, introduced through a straw, usually does a pretty good job.

FWIW...


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## kd3pc (Oct 19, 2006)

PalmettoSailor said:


> Are there brands besides the Mermaid folks would highly recommend?
> 
> The control unit on my AC/Reverse cycle heat unit was killed by lightning and rather than spend $800 on a repair, I was thinking to replace the unit as a DIY project since all the hard work (AC power, through hull, pump, ducting) is done.
> 
> Since I wasn't able to get a repair estimate before the start of this season I decided to suck it up until the Annapolis boat show to see if I could get a deal.


Flagship Marine (Marine Air Conditioning Systems - water, air and keel cooled.) has great gear that uses off the shelf contactors and relays, well built and competitively priced. Slip mate uses standard thermostat control on his and was easy to replace his old unit.


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## garyc919 (Jun 13, 2017)

Hello Everyone. My wife and I purchased a Bristol 35.5c in 2016 and I would like to install a Marine Air Conditioner. I am going to install a 16k BTU model anyone have any experience installing A/C in a Bristol? Where were you able to fit the unit? I am hoping it will fit under the port side settee or one of the hanging lockers on the starboard side. I know I am asking how long a short piece of sting is  but figured I would ask anyway.

Thanks
Gary


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## chuck53 (Oct 13, 2009)

garyc919 said:


> Hello Everyone. My wife and I purchased a Bristol 35.5c in 2016 and I would like to install a Marine Air Conditioner. I am going to install a 16k BTU model anyone have any experience installing A/C in a Bristol? Where were you able to fit the unit? I am hoping it will fit under the port side settee or one of the hanging lockers on the starboard side. I know I am asking how long a short piece of sting is  but figured I would ask anyway.
> 
> Thanks
> Gary


Are you having it done or DIY? If you are having it done, let your installer decide what works best.
If DIY, decide what unit you want, get measurements and figure out what works on your boat. You may have a couple of locations where the unit will fit, but how will those locations work with wiring, ducting and thru hull location.

Go up and read my earlier post #6. You probably have options.


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## garyc919 (Jun 13, 2017)

Hey Chuck,

Thanks for replying - I am doing this as a DYI project. I do have a couple of options for the install. I am hoping that I can install the unit under the settee. Once I am done with the install I will reply with what I did and hopefully some measurements for anyone else interested.

Gary


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## RegisteredUser (Aug 16, 2010)

From what I've looked at....

a) 110v window units in companionway or over a hatch. Relatively inexpensive and little work involved.
b) Portable 110v in-room ACs. Relatively inexpensive and little work involved.
c) Permanent AC system with a lot of work involved and hi $s with inherent maintenance and recurring costs. 

Take really hard look at the fans now available.
Also, take a look at a different climate....


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## FloridaBoy (May 4, 2014)

Hello Guys and Gals, I'm gonna have to go with RegisteredUser on this one. I bought a boat with a 16000 btu unit, professionally installed, about 4 years old when I inherited it. This is what I think about it. It takes up a lot of space on a boat with not much storage space. I redid all the ducting, two pieces, one to the v berth and one to a vent behind the port settee. Like RU said, it's got a seacock and a pump and an outlet for the cooling seawater. It also has condensate that drips into the bilge. I can't leave it running while away cause I'm afraid it will sink the boat if a hose clamp comes loose. All connections have 2 hose clamps, I'm still leery. It's REAL NOISY. It has a hard time cooling in the heat of summer because the water in the marina is so hot. Other times of the year it works better. I am not a liveaboard, I might think different if I was. My mates with one of those marine units on the hatch, seem happy and some also have one of those interior stand up ac units from HD. My biggest complaints are noise and taking up space. But they are all probably noisy. That's what I think. kevin


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## FloridaBoy (May 4, 2014)

Postal Script.... And it don't work if you ain't at the dock! kevin


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## Minnewaska (Feb 21, 2010)

There are pros and cons to an installed unit, for sure. Of course, you must either have a generator or be plugged into a dock or there is really no point. Because we typically anchor or swing into the wind on a mooring, we rarely use the ac off the dock. However, on a calm, humid day or to cool a room when taking a shower, it's very nice to have. Don't you hate getting out of a shower and immediately beginning to sweat before you even get new clothes on. When at our slip, wind will not necessarily blow down the hatches well, so it can be very nice to have.

We must close all shading on the port lights and hatches on a sunny, warm day, or the units won't keep up. The greenhouse affect of the glass will keep rewarming the interior. I also find that you want to set them at a temperature they can maintain. There is no point letting them run continuously or they will freeze. Automatic fan settings don't work well for a boat. They work best on the highest setting, which is definitely louder.

Technically, all ac units require maintenance. I think the home style units that are built into a hatch are just inexpensive enough that they are treated like they are disposable. My installed unit hasn't needed any repairs, but does get a bi-annual check over by the hvac dude. Roughly $75 for the cleaning and checkup. A couple of bucks more, if it needs gas added. Otherwise, (knock on wood) they keep on ticking. Personally, I find the exterior mounted units to be unsightly and I wouldn't want to climb over one that was installed in the companionway. That's a very personal choice, however.

Leaving thru hulls open is definitely a risk. Two clamps and inspect everything frequently is the best you can do. Many modern units have a feature that will dehumidify, rather than cool, while you're away. That very, very good to keep mold growth at bay. It's a trade off.


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## travlin-easy (Dec 24, 2010)

My 12,000 BTU marine air conditioner fits nicely beneath one of the dinette area seats, it is fairly small, cools my Morgan 33 Out Island from 90 degrees to 70 degrees in less than an hour and the only maintenance I perform is cleaning the filter and occasionally cleaning the raw water strainer. In the five years I have owned the boat, I replaced the raw water pump once with a self priming pump. 

Naturally, you must either have a genset to operate the AC while anchored, which can be a bit noisy if not properly installed. I tried a Honda 2000i and it failed a couple times when the AC recycled. I then want to an inexpensive genset from Harbor Freight that only cost $300 and it worked like a champ and no more noisy than the Honda. I saw a couple videos on You Tube where folks actually placed their gensets in a soundproof box and reduced the noise to a whisper and the genset did not overheat as some thought it would. 

Most of the time I use it tied to the dock, which is probably the most efficient method. The genset runs out of gas in about 6 hours, which is way too soon for an old codger like me. I tend to get up later in the morning.

Good luck,

Gary


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## flyingriki (Sep 27, 2012)

How many BTU's are sufficient for what sizes of boat? Wondering if just cooling the salon with cabin doors shut would work in nasty heat spells.


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## travlin-easy (Dec 24, 2010)

My 12,000 BTU cools the entire boat, a Morgan 33 Out Island, including the head, berthing area and quarter berth area equally and efficiently. This particular boat has more interior space that most 41 footers. A couple things come to mind, though. My boat is well insulated because of the balsa core in the cabin top, my hatch doors have both screens and lexan windows in them, and I have a ceiling vent in the head while allows the cold air to chimney through a grill in the bottom of the head door as the warm air exits through the ceiling vent. 

I have never been a fan of placing an RV air conditioner in the forward hatch of the boat over the Vee berth - just one more thing you cannot see over or around while underway. WM sells a 16,0000 BTU unit for about $1,600. You can find it for a few hundred dollars less at several online stores. From my point of view, especially boating in this part of the world, I would never own a boat that did NOT have a built in heat pump.

Good luck,

Gary


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## Tasmanman (Jun 30, 2017)

Hi Tony, I just listed an AC unit , the Cruisair 16000 BTU model. If you are interested lets talk. 
I just took it out of a Florida boat and it's all in excellent condition.
Regards
David


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## Tasmanman (Jun 30, 2017)

Hi Tony, if you look in the forum I just posted a Cruisair AC unit for sale, everything is there that you need, I just took it out of a boat from Florida that I brought to the Northwest.
Let me know if you want more info and maybe we can work something out.
Regards,
David Vohs


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