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Jet Ski Closed Loop Cooling VS. Open Loop Cooling Debate

One of the biggest questions I get when I’m selling Sea-Doo 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.

seadoo corrosion closed loop cooling system yamaha

There use to be no debate

There use to be a time when everyone used the open loop cooling system, even Sea Doo. Back when Sea Doo made 2-stroke jet ski’s 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 for jet skis.

How it 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.

There is another option to cool the engine, air-cooled, but the problem with this is that you don’t get much airflow in the engine compartment of a watercraft. The air-cooled engine works great for lawn mowers but not so great for a jet ski. 

Open Loop

Using lake water to cool the engine is a great idea, unlimited cooling supply for the engine. It’s also a little simpler since its just sucking in the water that’s around it. The biggest problem with open loop is that it’s sucking in water that’s around it.

So if you’re riding in the ocean you’re sucking in salt water which is very corrosive to the engine. Riding in the ocean requires you to flush the engine more often. That once easy to maintain open loop system gets an extra step to make sure your engine doesn’t corrode. The water that goes into the engine goes around the cylinder walls to cool the engine and since the engine is made of metal the salt in the water will slowly corrode the engine from the inside.

The corroding from the inside out is lowered when you ride in a lake or river since it doesn’t have much salt to it. But lakes and rivers still have corrosive minerals in the water that still can corrode the engine. Don’t panic, when I say corrode it can take years to see any effect.

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 can expand enough to break metal. With an open loop you just have to be cautious when freezing weather comes as to make sure the engine block won’t freeze and damage the engine.

One last thing about open loop cooling is that it not only takes in water but also whatever is in that water. So all that pollen, sticks, leaves, and whatever else is in the water will also be pulled into the cooling system. Just like how arteries can get clogged when you put junk into your body so can your jet ski cooling system get clogged when you run in dirty water. A clogged cooling system can mean the engine will run hotter and have to work harder.

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Closed Loop

Closed-loop cooling system (Sea-Doo ONLY) works much the same as an open loop system but instead of having water flow into the engine to cool it, antifreeze is used instead. The antifreeze is circulated through the engine than to a ride plate. The ride plate is just a heat exchanger or a radiator that converts the hot antifreeze into cool antifreeze.

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. Colder antifreeze is pumped back to the engine to cool it.

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 exact same system as a Sea-Doo watercraft use. So if your car uses it why wouldn’t your jet ski?

On top of all that since its 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.

Also since you don’t have water near the engine winterizing is even easier. No need to flush the engine on a Sea-Doo since it is completely sealed up. But there is one drawback! The engine is completely sealed up but the exhaust and intercooler are still cooled by water and they will need to be flushed out for winter.

One big perk with the closed loop cooling system is that it can be controlled to keep the engine at a perfect temperature at all times. Where the open loop system can not. So if it’s extra hot that day the water will be extra warm too. Warmer water for an open loop system means the engine runs warmer which relates to you burning more gas and do more damage in the long run to the engine. Due to the nature of a closed loop system, warmer days have no effect on the engine.

To Sum It up

To sum it all up I’ve listed below the pluses and minuses of both.

Open Loop

Plus – Simple older technology that seems to be still very common in boats.

Minus – Takes in corrosive water and debris that could clog the engines cooling system. You must winterize the engine block.

Closed Loop

Plus – Don’t have to worry about corrosion on the engine block or debris clogging the engine. The same system that your car uses. Don’t have to flush the engine block since it never sees water.

Minus – The exhaust and intercooler need to be flush when winterizing.

36 thoughts on “Jet Ski Closed Loop Cooling VS. Open Loop Cooling Debate”

  1. 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?

    Reply
    • 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.

      Reply
  2. 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.

    Yousef

    Reply
  3. 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?

    Reply
    • 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 https://www.youtube.com/watch?v=Grd6IwYpdo4. 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.

      Reply
    • 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.

      Reply
      • 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

        Reply
  4. 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.

    Thanks

    Reply
  5. 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.

    Reply
    • 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.

      Reply
  6. 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?

    Reply
    • 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.

      Reply
      • 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

        Reply
        • 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 https://www.youtube.com/watch?v=sDB6gnyfgM8

          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.

          Reply
        • 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.

          Reply
      • 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.

        Reply
          • 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

  7. 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.

    Reply
    • 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.

      Reply
    • 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.

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

    Reply
  9. 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?

    Reply
    • 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.

      Reply
  10. 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.

    Reply
    • 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.

      Reply
    • 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.

      Reply
    • 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.

      Reply
    • 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.

      Reply
      • 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.

        Reply

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