Closed Loop Cooling VS. Open Loop Cooling Debate

One of the biggest questions I get when I’m selling Sea-Doo’s is the closed loop and open loop cooling debate. Which one is better? Does this require more maintenance? My buddy says that _____. You get the idea.

I’m hoping to shine a little light on this debate and hopefully help you decide on which one you think is better for your needs.

seadoo corrosion closed loop cooling system yamaha

There Used To Be No Debate

There used to be a time when everyone used the open loop cooling system, even Sea-Doo.

Back when Sea-Doo made 2-strokes it was normal for that ski to be cooled by the lake or ocean.

Then in 2002, Sea-Doo released the 4-Tec engine, which is a 4-stroke engine that has a closed loop cooling system to it. So, this is really where the debate begins for the closed loop vs open loop.

The Difference Between Open Loop Vs Closed Loop Cooling

The main difference between open loop and closed loop cooling is how the engine cycles a coolant to keep the engine cooled.

Open loop cooling uses surrounding water to keep it cooled, while closed loop uses antifreeze in a sealed environment with a heat exchanger. The open loop system is constantly cycling new water from its surrounding, while the closed loop is cycling the same antifreeze and using a heat exchanger to keep it cooled.

How Open Loop Cooling Works

The way open loop cooling works (found on Yamaha and Kawasaki) is that it takes in lake or ocean water to cool the engine. Your engine needs to be cooled, or it will run so hot that the metal could fuse and stop the engine.

The water is pumped from the jet pump, there is a little hole that the impeller pushes some water through. This water cycles around your engine block and other parts that get warm, like the exhaust.


Open loop cooling has its pros, here are a few of them.

  • Unlimited cooling supply.
  • Simpler.
  • Less weight.
  • Can run cooler if the water temperature is low enough.

Using lake or ocean water to cool the engine is a great idea, unlimited cooling supply for the engine. It’s also a little simpler since it’s just sucking in the water that’s around it.

While open loop cooling is simpler and has a larger cooling supply to pull from, it has a few downsides we need to cover.


The downsides to open loop cooling for a watercraft are quite concerning:

  • Takes in surrounding water (saltwater).
  • Cooling is not as constant and depends on the water temp.
  • More water intrusion.
  • Clogging due to debris in water.
  • Air pockets get trapped.

The first one about open loop taking in the surrounding water is a big one, especially if you ride in the ocean. The engine takes in the surrounding water, and saltwater is very corrosive.

The cooling is heavily dependent on the temperature of the water and not as constant. Water temp in some areas will not be the same as others, so the engine isn’t getting the same constant supply.

Since the open loop system requires water to be pushed to many places inside the ski, you have more chances for waterlines and connections to fail. The more water lines you have and connection points, the more chances of failure and for the jetski to take on water.

Lastly, since you’re taking in any water that is around your craft, you’re also taking in any debris too. Sticks, mud, pollen, pollution and anything that can gum up your cooling system will gum it up. You must keep an eye on the “pisser” to make sure the PWC does not have a clog.

Also, since the open loop system takes in water to cool the engine, you also have to worry about winterizing the engine block. When water freezes, it expands and this can crack your engine block.


I know some say open loop is “maintenance-free” but it’s not, you still need to clear out clogs and flush the waverunner.

Open loop has less maintenance than a closed loop system, but it’s not maintenance free. With open loop cooling, you need to take extra care when flushing your PWC, as you have more contamination to remove than closed loop.

The maintenance you do on a closed loop cooling system is not that hard, it’s about similar to the maintenance you do on your car.

How Closed Loop Cooling Works

gti closed loop cooling ride plate

A closed-loop cooling system (Sea-Doo & Rotax engines ONLY) uses antifreeze to cycle it around and through a ride plate to keep the engine cooled.

Closed loop cooling is the same system your car uses to keep its engine cooled, but instead of a ride plate, your car uses a radiator. Your car uses passing air to cool the radiator, and a watercraft uses passing water to cool the ride plate.

Closed loop cooling is so nice that many boats on the coast switch to closed loop.

The way the ride plate works is that it allows the antifreeze to circle around in the plate. While circling around, the antifreeze is being cooled by colder water touching the ride plate. The heat transfers from the antifreeze to the ride plate and is carried off to the water. The now cooler antifreeze is pumped back to the engine to cool it and repeat the process.

See how the Sea-Doo engine works with the closed loop cooling towards the end of the video below:


Closed loop cooling has many positives features:

  • Closed off system, no outside water.
  • Don’t have to worry about debris.
  • Constant cooling.
  • Fewer chances of leaks from exterior water.
  • Winterizing can be easier.

Now you might be thinking, how reliable is this closed loop cooling system? It’s so reliable that all modern cars, planes, and even trains use it! Yes, the car you drive into work uses the same system as a Sea-Doo watercraft.

On top of all that, since it’s a closed system, you won’t take in any corrosive water. Since you don’t have anything eating away at the engine block of a Sea-Doo, you could have the engine last much longer.


While closed loop cooling is great, it has downsides we need to cover.

  • Still needs to be winterized.
  • More maintenance.
  • Not 100% closed off.

The biggest confusion about closed loop cooling is that people think it doesn’t need to be winterized, this is false. While it’s true, the engine is sealed up, you still must do a few storage procedures to make sure the watercraft is stored away proper.

We can’t ignore that a closed loop cooling system will need more maintenance than an open loop system. The antifreeze does wear out, leak, and must be tuned up every so often. Just think about your car and how often you deal with the cooling system on it as It’s mostly the same, just that the PWC is used less often, so it might not be as often.

Lastly, and the honest truth, the closed loop cooling is not 100% closed off. The engine block is only getting antifreeze, but the exhaust and supercharger (if you have one) still take in outside water. This is why you still need to winterize a Sea-Doo even though it uses a closed loop cooling system. Not only that, but Sea-Doo does have units with iBR that are cooled with lake or ocean water, as they generate a lot of heat.

Even though a Sea-Doo is a closed loop system, you should still flush it after riding in salt or dirty water.

Winterization – Everyone Needs To Do It!

No matter if you have a PWC with a closed or open loop cooling, you still must winterize it.

All jet skis, even closed loop, still take in water to cool the exhaust, and intercooler if it has one. Some even use water to cool the braking system or rectifier, as they can run hot.

If it gets below 40F/5C where you live, you should winterize it. There is also a de-winterize process, but it’s super easy to do in comparison.

Buying – Open vs Closed

If you’re buying a jet ski and stuck on the open loop vs closed loop cooling debate, don’t be, there are far more important factors to consider.

For example, here are more features I consider more important:

  1. Price.
  2. Does it have brakes and neutral?
  3. Top speed.
  4. MPG.
  5. Dealer markup.
  6. Monthly payments.
  7. Will it fit in my garage?
  8. What it’s going to cost to own a jet ski.

There are perks to both systems, but there are far more important factors to consider when buying a jet ski over how it’s being cooled.

Air-Cooled Sea-Doo Engines

Air-cooled watercraft are not a thing anymore, the first Sea-Doo was air-cooled but when they became mainstream, they moved to open loop cooling.

Check out what the first Sea-Doo looked like in the video below:

The first Sea-Doo was only 18HP, the smallest machines today are at least 90HP with a few going over 300HP! One of the biggest problems for this early Sea-Doo was that it could not get enough airflow to cool the engine.

The Reason For A Cooling System

All engines need some way to keep themselves cooled as they take in fuel to burn and create the engine to move the vehicle.

Smaller engines can get away with being air-cooled like your lawn mower, but the more power the engine has, the more it needs to be cooled.

A gasoline engine that is being cooled runs better and more efficient than one that is running hot. All models will have an alarm system to warn you when the engine is too hot, with most of them shutting the engine off at a certain point.

Jet Boat Engine Cooling

Sea-Doo didn’t give closed loop cooling to only their watercraft line up, but they also had it on everything that used the 4-stroke engine.

This means the 4-stroke Sea-Doo Jet Boats, Sea-Doo Switch, and any boat manufacturer that had the Rotax engine. Rotax is own by BRP, who also own Sea-Doo, and the engines were sold to many boat manufacturers, especially after Sea-Doo got out of the jet boat market in 2012.

There was a time when Chaparral had jet boats that used the Rotax jet drive engine, and Scarab still carries on with it.

Sea-Doo got back into the jet boat market with the Sea-Doo Switch, which I reviewed here, it’s a jet-powered pontoon boat that is really shaking up the pontoon world!



I started working at a power sports dealership in 2007, I worked in parts, service counter, and as a technician before moving to sales in 2013. I created in 2014 to answer common watercraft questions I would get from people. Now managing the site full-time, I continue to provide advice and web tools for my readers about watercraft. I've owned several watercraft, with a Sea-Doo Spark as my current main PWC.


  1. Steven,

    Thanks for all your good information. I have 2 seadoo LRVs. One has a rebuilt 951 and runs 50 mph. The other has never been touched. I have it set up for fishing and it normally does 45 mph. Took it to Florida and got in some real shallow water … not on purpose. What I did not know was sand blocked the outflow tube. Engine did not seem to overheat but speed was only 36 then dropped to 26 and had smoke inside engine bay. So I think my tuner pipe was real hot if not the engine also.

    So my question, I bought the second ski for fishing with the intent of putting in a 4tec without turbo with highest HP I can. Is the 155 hp the best? What do you think? I want to keep it as simple as possible and do not need to go 70 mph … (too fast for trolling)


    • LRV is not something I see much these days. I heard of people doing a 4-stroke conversion on them but I have never seen it in person. You got plenty of room in the LRV that is for sure. I would stick with the 155 for sure if you want to keep it simple.

  2. I just purchased a 2003 Seadoo GTX 4Tec with 199 hours. Ran great on the water test. I’m just curious how long it takes the engine to cool down after use. Got back to my house about 1 hour later and took the seat cover off and it was still a bit warm. Is that normal?

    • It’s not unusual for your jet ski engine to be warm after an hour of sitting especially if you rode for a good bit. If you’re worried you can always take it to your dealer and let them hook it up to see if there are any fault codes like a bad temp sensor.

  3. Hello steven, me and my friend are lookin to buy 2020s limited, i like seadoos i like the look of it and the link system, my friend is aiming for yamaha but i am afraid cause all i hear is sea doos not as reliable, should i just take a yamaha with him instead? or seadoos not reilable not true

    Sorry for my english.


  4. Hey Steven. I drained my cooling system via drive plate screw. I then added cleaner and distilled water and ran boat in lake. I’ve been drained that and added 50/50 XPS coolant. I only ran the engine for a couple minutes and I doubt the thermostat opened. Am I safe for winter?. Does the whole cooling system drain ragardless of whether the thermostat is open or closed?

    • You don’t drain the coolant from the ride plate. You flush with RV antifreeze through the input hose in the rear as this video shows You’re going to need to take your jet ski into the shop and let them flush the coolant system and add the correct coolant back. The ride plate already had the correct antifreeze in it from the factory and should not be touched. When you flush a jet ski for the winter you’re removing the water that is in the exhaust and if you have a supercharged model it’s removing it from the intercooler too.

    • Steven. I got your response. I already winterized the exhaust system, that’s different. The closed-loop cooling system should be flushed every two years. That is what I’m talking about.

      • Thank you. When I refilled the system I don’t think I got it up to where the thermostat opened so I just want to make sure there wasn’t water sitting in there. But it sounds like when you drain the system everything drains out

  5. Why doesn’t blowing it out with air force the water into the block? After I did the air and thinking about it I looked into the cylinder and oil and didn’t see signs of water when I fogged it. Should I be concerned at this point?

    Next year I will take your anti freeze suggestion, it sounds like a better way.


  6. why do you start the engine before turning on the hose? is it because water will flow from the muffler into the exhaust ports on the block? someone told me to blow it out through the hose connection to winterize it but wouldn’t that blow water from the muffler into the block?

    Thanks- this thread is great and very educational.

    • Yes, not having the engine on when you turn on the water hose will fill up the exhaust and that will then dump into the cylinders. Since there is not a good place for the water to go when you try to turn on the engine you could bend a rod and blow the engine. Jet skis have a flush adaptor somewhere that you hook up a hose to. This connection can also be used to winterize or flush it with marine anti-freeze. Many of the owner’s manuals say to use compressed air to blow it out but I like to use Marine Anti-Freeze to winterize my stuff. I turn on the engine, grab my funnel and hose and I pour in a gallon of the pink RV/Marine Anti-Freeze in. I remove the hose and short burst rev the engine to get out the extra anti-freeze.

  7. Hi Steven,

    Your articles are awesome. Thank you.

    I am looking for a new PWC. First time buyer. Long-term reliability is a major issue for me.

    In your view, are the Sea-Doo normally aspirated engines (e.g., GTI 130) very reliable?

    • I consider the 130HP and 155HP engines from Sea-Doo to be one of their best ever engines made. They had a rough start when they came out in 2002 but from 2004 on they’ve been rock solid in my personal experiences.

      • Hi Steven, I’m kinda confused on the seadoo engines. We r looking at a 2017 GTR-X 230 so has super charger on it and a 2016 GTI 155 with no super charger. We r in fresh water all summer but take our WaveRunner to the intercoastal for winter. Which engine in your option would handle both the best, including ride in intercoastal and engine wear as well as maintenance? Thanks Susan

        • Both will handle the saltwater fine, it’s just that the GTR-X uses ocean water to cool the intercooler which is not a huge deal. The only thing that matters the most is you winterize it if it gets below freezing where you live for more than 24 hours and flush it out when you leave the saltwater. This video shows you how to flush your Sea-Doo

          If you want something with the least maintenance the GTI 155 will be the one to get because it has fewer moving parts. Both will ride the same as they both have the same hull but the GTR-X will be noticeably faster especially at take-off.

        • I have a 17 year old Sea•Doo with the 155hp engine, and it is a solid work-horse. It’s the biggest engine Sea•Doo offers without a super-charger, and it’s more than you need. It will take you 60mph and is pretty much maintenance free. I keep the oil changed, but the maintenance is on the water pump (impeller, wear ring, etc), not the engine. I think the 155hp engine in the Sea•Doo is the single best engine ever offered on any pwc.

      • You probably should say “from 2003 on” because my 2003 GTX with the 155hp engine has been a great machine. It has over 500 hours on it, and it has shown no signs of letting up. The only maintenance has been oil changes, and the rest has been to the water pump (I’ve changed the wear ring, but still have the original impeller). This ski has been ridden by all kinds of riders…friends, kids, and the worst rider of all…teen aged girls! I have no reason to ever buy anything but Sea•Doo.

          • Get the 230 if you can afford little more in maintenance in the long run. The 230 is a beast and has just the right amount of power if you like to go fast at times but still get decent fuel economy when riding conservatively. Just something about forced induction changes the characteristics quite a bit to make it a lot more fun. If you really want to go fast from a stop go with the 300. It’s about another $3000 over the 230. Same top speed due to coast guard agreements but will get you to 60 in about 3 seconds versus 4.5 with the 230. You’ll literally feel like you’re getting ripped off the 300 because it’s so fast. The 230 is the best middle ground for most people before it starts to be too much for a lot of riders. They’re all great fun whatever you choose. I just don’t recommend going any less than the 170. I have a RXT-X 300 personally and it’s great fun and very reliable. I just follow the maintenance schedule. My buddy has a GTR 230 and it’s just as much fun for 95% of the same riding. It just doesn’t have that extra acceleration. But it’s fun to have when if you’re a speed freak and adrenaline junky. The Rotax engines in the Seadoos are the best out there. I also have a buddy with a Scarab jet boat with twin supercharged 250 hp Rotax engines (same as Seadoo) and he’s had zero issues with it in the 5 years and 250 hours he’s he’s used it. His was built before 2017 so at the 200 hour mark he had to have the superchargers rebuilt at a cost of around $1000 each. But the 2017 and newer engines got a different supercharger that don’t have to be rebuilt because of a redesign. I think the same went for the supercharged Seadoos before 2017. Hope you have fun with whatever you choose. Just stay away from the Yamaha and Kawasaki’s if you use it in salt water. Otherwise Yamaha is another brand to consider cause of their reliability. I haven’t heard the best things about Kawasaki. But there’s a reason why Seadoo is the most popular maker of PWC’s

  8. Steven, I enjoyed the article, but I think you are missing a big point. Open loop systems are used by manufacturers of marine-specific engines. Even BRP’s own Evinrude uses an open loop system in all of their motors because they are marine-specific. Sea-Doo uses closed loop because they have to. They use the same Rotax engines that their Can-Am 4-wheelers, and Ski-Doo snow mobiles use. You will see that Mercury and Volvo inboard/outboard motors are closed loop because they are designed using car motor blocks. Mercury outboards use open loop because they are designed for marine use. Something like 80-90% of saltwater outboard boats use Yamaha motors. Closed loop systems are significantly more complex, harder to winterize, and harder to service. So, the choice is between Ski-Doo with a complex motor that was modified for marine use or a Yamaha, whose motor that was designed exclusively for marine use. Ask any saltwater off-shore fisherman and they will tell you to buy Yamaha.

    • Actually, the Sea-Doo 4-tec engines are vastly different than what’s in a Can-Am. For instance, the Can-Am ATV uses a V-Twin and the Sea-Doo uses an in-line 3 cylinder. Only the Sea-Doo Spark uses the same engine block that can be found in a snowmobile, but the same thing can be said about Yamaha and Kawasaki too. Yamaha and Kawasaki have been known to repurpose motorcycle engines for there jet skis. For example, the Yamaha MR1 is the R1 motorcycle engine and the Kawasaki Ultras are based off the ZX12 engine.

      Mercury also uses a Chevy Engine block for there inboards/outboards, which many use the open loop cooling. You can buy these engines with closed loop cooling systems but many don’t unless you keep it in salt water all the time. The Sea-Doo 4-tec is about the only marine purpose engine on the market along with Yamaha TR-1, these engines were not repurposed.

      When it comes to jet skis the maintenance required for closed loop is not complex. The service intervals are much longer and the average person never even has the jet ski long enough to get those points. It’s like your car, you change the oil more often but the coolant gets changed in much longer intervals (some people never even change it especially if they have the high mileage coolant that Sea-Doo started using years ago). For winterizing its not more complex since it’s already got anti-freeze in it.

      When it comes to outboards, I agree that open loop is the way to go because of how it drains and the weight constraints. And Yamaha makes some of the best outboards on the market, I can’t argue that. But for jet skis, I’ve found closed loop works better for the average owner.

    • I have a 17 year old Sea•Doo, and I’ve never even serviced the closed-loop system. I did flush the radiator once, just because I felt I should, but to say they’re more difficult to service is just not true. As for winterizing, I don’t do anything here in NC. I pull it up on the ride-up lift and squeeze the trigger before shutting it off. Winterizing is much more critical on open loop systems like you find on my Ski Nautique. If I don’t drain the engine block, out winters are sometimes harsh enough to crack the engine block. My buddy has 2 very nice Yamaha jet skis, but he has a problem when we have hot summers. He kept taking them in for service a couple summers ago because he couldn’t figure out why they were running hot. Turns out nothing was wrong, it’s just that our water got too warm to cool them. My Sea•Doos we’re running in the same lake (Lake Norman) with no issues. That is what really sold me on closed loop systems.

    • Sorry, but you don’t know what you’re talking about. The Rotax engines used in Sea-Doo are NOT used in any other product types (with the exception of the 900cc engine in the Sparks), they are designed and built specifically for watercraft. Secondly, outboards are not suited to the inclusion of a heat exchanger system, hence they remain open loop at this time. Steven is correct in everything he says, but he did miss the fact that the closed loop system utilizes a thermostat which ensures the motor comes up to design temperature quickly and holds it there for optimum engine performance and efficiency. I’ve seen enough open loop engines in pieces with water galleries full of silt to know which is the better system.

  9. Open loop systems for boats still have a thermostat to control water flow for optimum engine running temperature.

  10. Thanks for all the info on open/closed, it has been helpful. I have a 2006 215 up supercharged sea doo sportster, I have been trying to determine if the supercharger has lake water in it, or if there is.a separate cooler for it…it appeaappears to use antifreeze? Any comments?

    • Supercharged Jet Ski engines take in lake or ocean water to cool the intercooler. So your Supercharged Sportster takes in lake water for the intercooler.

  11. Does that mean that I should be able to dock my Scarab 165 in the marina (keep it in the water) without taking it out of the water to flush it regularly? It is salt water.

    • Then engine uses coolant to keep it cool but the exhaust takes in ocean/lake water to cool and muffle it. If you have a supercharged model then the intercooler does take in ocean/lake water to cool that. It would be best to side on caution and flush it regularly. If you can look into dry storage or the docks that lift the boat out of the water to keep algae and scum from building up under any boat too.

    • They could corrode if used in constant salt water without being flushed, but it would take a long time. Those components are made of aluminum and corrosion is not quick with aluminum. Only Sea-Doo’s with superchargers (over 155hp) have intercoolers. The exhaust is an aluminum water tank and the 2 reasons why it takes water in is to cool the exhaust and to muffle it.

    • Salt water still cools the intercooler and exhaust. Seadoo has a known intercooler failure problem from minor corrosion and have been through several revisions. All said and done it is a much better system than Kawasaki offers in their skis.

    • Message: Hi Steven,

      Thank you for your informative website.

      My question – that I think other sea-doo and other ski owners might be interested in is this: I have a gti 170 2020 seadoo. I just got a lift and I’m worried that the lift isn’t tilted/raked enough to allow for proper drainage when I flush and wash engine bay. Will the ski drain ok if it’s level or must be tilted a bit? I was thinking I might need tapered bunks to compensate.

      • Interestingly enough the optimal position for any jet ski is flat/level and not tilted. You do not want to tilt it when on a lift. Jet ski manufacturers design them to drain when level and not tilted because this is how they sit when on lifts.


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