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.
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-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.
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 Pros:
Open loop cooling has its pros, here are a few of them.
- Unlimited cooling supply.
- 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.
Open Loop Cooling Cons:
The downsides to open loop cooling for a jet ski 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 jet 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 jet ski to take on water.
Lastly, since you’re taking in any water that is around your jet ski, you’re also taking in any debris too. Sticks, mud, pollen, pollution and anything that can gum up your jet ski will gum it up. You must keep an eye on the “pisser” to make sure the jet ski does not have a clog.
Open Loop Maintenance
I know some say open loop is “maintenance-free” but it’s not, you still need to clear out clogs and flush the jet ski or 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 jet ski, 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
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 jet ski 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 Pros:
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.
Closed Loop Cooling Cons:
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 jet ski 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.
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:
- Does it have brakes and neutral?
- Top speed.
- Dealer markup.
- Monthly payments.
- Will it fit in my garage?
- 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 Jet Ski Engines
Air-cooled jet skis are not a thing anymore, the first Sea-Doo was air-cooled but when jet skis 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 jet skis 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.
Why Do Jet Skis Need 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 jet skis 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.
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!