Jet skis are not all 2-stroke. Most jet skis are 4-stroke, as the 2-stroke units have gradually faded from the market. There are two types of engine options for a jet ski: a 2-stroke engine and a 4-stroke engine. The 4-stroke engine is now essentially universal.
If you are looking at used jet skis, you may have come across a lot of 2-stroke jet ski models. They aren’t worth much anymore, as 2-stroke skis are very old.
Sea Doo, one of the leading manufacturers of jet skis, phased out the 2-stroke engine in 2007. Yamaha and Kawasaki both sell just 4-stroke skis, as well.
What is A Combustion Engine?
Before we get into the nitty gritty of different kinds of engines, let’s talk about what the general makeup and function of an engine are. A gasoline powered combustion engine works in a cyclical nature. The piston within the engines moves up and down (the top position the piston reaches is called TDC, meaning Top Dead Center, and the bottom-most position the piston touches is called BDC, Bottom Dead Center.)
Then there are the valves. When a piston is in the TDC position, it is closest to the valves. When the piston moves into BDC position, it is furthest away from the valves.
What is a Stroke?
A stroke is when the piston in an engine (mentioned above) moves from the TDC position to BDC position, or the other way around. Think of it as a swimming stroke: your arm glides through the water from the top of your body, downward, to propel your body through the water. A stroke in an engine is similar (in theory.)
The full combustion cycle entails gas and air being thrust into the piston, igniting it and then pushing out the exhaust. The critical difference between a 2-stroke engine and a 4-stroke engine is how fast the combustion cycle occurs.
This is directly determined by the number of times the piston moves up and down during a given cycle.
A 2-stroke engine’s piston moves up and down only one time within the combustion cycle, whereas the 4-stroke engine’s piston moves up and down two times during its revolution.
PROS
- Light Weight: a jet ski with a 2-stroke engine is going to feel a lot lighter and easier to manipulate than the 4-stroke engine
- Easy to Repair: due to the 2-strokes simple design, a 2-stroke engine jet ski is going to be much easier to fix. This is ideal for the DIYer who prefers to repair their own motorized toys.
CONS
- Loud: The 2-stroke jet ski is, unfortunately, going to have an audible high-pitched whizzing sound.
- Shorter Lifespan: Due to the 2-stroke engine having more torque in higher RPMs, this means the engine will wear out long before a 4-stroke engine will. The high RPMs take a heavy toll on a motor.
- Requires Pre-mixing: A 2-stroke engine requires the pre-mixing of oil and fuel, whereas the 4-stroke engine does not.
- Causes Pollution: Unfortunately, the biggest down-side I’ve come across personally is that this type of engine is pretty terrible for our waters. About 20-25% of the fuel in a 2-stroke engine does not burn, which means it is left to leak into the water around if.
- Less Readily Available: Due to certain jet ski manufacturers no longer selling 2-stroke jet skis, you will likely have an easier time purchasing a new 4-stroke. However, you will be able to find many used 2-stroke jet skis.
- Parts not available: They may be easier to work on, but you still need replacement parts. Most people now are pulling parts from used 2-stroke skis to replace broken parts. Those will also wear out and eventually there will be no more spare parts.
The 4-Stroke Jet Ski Engine
PROS
- Efficiency: considering the fact that the fuel in this type of engine is being consumed every four strokes, the 4-stroke engine is by far more efficient. This type of motor is used more frequently in larger vessels (like a jet ski), whereas you can find a 2-stroke engine in smaller items, like a chainsaw.
- Less Noisy: the 4-stroke engine is naturally going to be quieter than your 2-stroke engine.
- More Environmentally Friendly: while any motorized craft will inevitably pollute in some form or another, the 4-stroke jet ski will effectively be 30% more environmentally friendly than its 2-stroke counterpart.
- More Durable: the 4-stroke engine is more durable and has better longevity.
- New & Available: Since most new jet skis today are 4-stroke, they are going to be more readily available and easy to find. If you purchase new, most retailers will provide you with a 2-year warranty.
CONS
· Heavy: A 4-stroke engine is going to be nearly 50% heavier than a 2-stroke engine, and depending on the rider and their skill sets/needs, this could make a big difference. (The Kawasaki brand 4-strokes is likely to be the lightest 4-stroke option on the market
· More Expensive: The 4-stroke engine jet ski has more parts (including valves), and the repairs cost more than the 2-stroke engine. However, these out of pocket costs shouldn’t be too much of a concern when you first purchase, as your craft will be under warranty (if you purchase it new).
The Takeaway?
Truthfully, you are likely to have an insane amount of fun on either a 2-stroke jet ski or a 4-stroke. The watercraft of your choice really depends on your individual needs.
If you are looking for something cost-effective, then you may want to purchase a used 2-stroke (just be aware that you may need to repair it more frequently – and that could potentially cost you $500-1000 per repair).
If you desire something that is new, ready to go, and under warranty, you’ll want to purchase a 4-stroke jet ski at your local retailer. Here are 10 things to look for when buying a used jet ski.
And if you want a lightweight stand up ski, the Yamaha Jet Blaster now captures that market. For a light sit down model, the Sea Doo Spark Trixx is a blast to ride, as well. We love ours.
Final Thoughts
Most new jet skis sold today have 4-stroke engines. And the market for specialty accessories has grown to the point you can outfit your ski for all different types of use. Regardless of engine size, the goal is to have fun, and when you’re riding your jet ski, you won’t be thinking about the number of strokes, but how much fun you’re having.
