If your jet ski is not reaching its normal top speed anymore it can be super annoying!
Maybe your jet ski is off by a few MPH, or perhaps it’s off by 10MPH or more! Either way, you need to know why.
There are several reasons why your jet ski may not be reaching its top speed anymore. I want to list off the most common reasons for a jet ski to be lacking in its normal top speed and what you can do about it.
Reasons Why Your Jet Ski Is Not Reaching Its Top Speed
Here are the more common reasons why your jet ski is not reaching its top speed anymore:
- You’ve sucked something up.
- Damaged jet pump.
- Supercharger failure or loose hose.
- Wrong key.
- Wrong driving mode.
- Still in break-in mode.
- Not trimmed right.
- The Speedometer lies.
- Bad gas.
- Bad spark plugs.
- Blown engine.
This list is gear more towards 4-stroke jet skis, if you have a 2-stroke some of this will still apply to you, and if none of the above work, then it’s probably your carburetor, and it needs to be cleaned or replaced.
Let’s go over each point and show you want you can do to get your jet ski back up to speed!
1. You’ve Sucked Something UP
The most common problem people have with a jet ski is sucking something up.
Rocks, sticks, sand, and everything in between can get sucked up into a jet ski and cause all kind of running issues.
So, if your jet ski is not reaching its top speed, I would check the pump to make sure you haven’t sucked something up.
2. Damaged Jet Pump
Usually, sucking something up leads to damaging the wear ring and/or impeller, which is a part of the jet pump.
Though, you can get a damaged jet pump in other ways.
One way is a damaged through-hull seal, which can keep your jet ski from reaching its normal top speed.
Inspect the jet pump for any damage, it will require you to remove the pump to fully see the problem. Some parts of the jet pump require special tools, so you may need to let a repair shop do this for you. But you can look through the intake and rear for anything that is out of the normal.
3. Supercharger Failure Or Loose Hose
If you have a supercharged jet ski, which is most engines that are over 200HP, and the supercharger fails, it will keep you from hitting top speed.
Where your jet ski may have done 70MPH before, but will only do 60MPH now, is a common example of a supercharger that has failed.
One thing to look out for is the supercharger hoses have not blown off. I’ve seen this quite a bit, as the superchargers put out a lot of pressure. Look around the rear of the engine for the supercharger hoses and make sure they’re not loose.
If you have a supercharged jet ski you need to check it for boost, but most often if you have a supercharged jet ski, and it’s not going above 7,000 RPMs then it’s most likely your supercharger.
4. Wrong Key
Sea-Doo, Yamaha and Kawasaki all have key options that control the power of the watercraft.
For example, Sea-Doo has a learning key that limits the top speed from 32MPH up to 50MPH, depending on the model and how it was programmed.
Yamaha has key fobs and Kawasaki has similar keys to Sea-Doo, they all can limit the power of the jet ski.
It’s quite common for people to forget that these keys exist and grab them because they lost their normal key. So make sure you don’t have a slow key or the fob set to a slower speed.
There is even a rental key that limits the jet ski to 45MPH. If you bought a rental jet ski, make sure they made the key fast and removed any other limiters that their insurance company makes them have.
5. Wrong Driving Mode
Just like the keys, most jet skis have different driving modes.
You have touring, sport, ECO and many other names.
What is interesting is that these driving modes are more about slower take-off than affecting top speed. But some modes like ECO will limit top speed from 40MPH to 50MPH.
Make sure you’re not in a different mode that is limiting your jet ski’s top speed, it will clearly state the mode on the display.
6. Still In Break-In Mode
It’s becoming more common for new jet skis of all sizes to have a break-in mode. Even the lower horsepower jet skis still have high-performance engines, and proper break-in is important.
Not many people do engine break-in properly, so the manufacturers are now doing forced break-ins. This means the engine is not fully unlocked, and you will not get to top speed for a bit.
Usually, after the first 5 hours the engine will unlock itself, but it can go up to 25 hours to fully be broken-in or could happen after the first service. The more HP your jet ski has, the more the break-in is forced.
7. Not Trimmed Right
If your jet ski has trim, sometimes called VTS on Sea-Doo, make sure you have the trim set correctly.
If you’re drag racing you want the trim all the way down, then when you get on plane, raise it up.
Don’t trim all the way up or the jet ski will want to jump out of the water.
Every jet ski is different, you will need to find the sweet spot for your trim, the wrong trim height will affect top speed.
8. The Speedometer Lies!
If you’re sweating over a few MPHs, then the honest truth is that the speedometer can lie.
The speedometer on a lot of jet skis is not accurate at all.
Some jet skis do use GPS to get their speed, but even that can be fudged a bit or get off due to cloud cover.
It’s the RPMs that matter, not the speed. It’s when the RPMs are not what they used to be that you need to worry.
I’ve even had people confuse the KPH with MPH. One guy swore his jet ski used to do 100MPH, and now it only does 60MPH. Come to find out, it was originally set in KPH, and 100KPH is about 60MPH.
9. Bad Gas
Gas isn’t what it used to be ever since they started adding ethanol, and it’s been super annoying for boats.
If you did not put stabilizer in your gas when storing your boat for months, there is a good chance the gas has gone bad. Bad gas can lead to all kinds of running problems, especially with supercharged engines.
If the gas tank is under a half a tank, put some premium gas in and see how it responds. Add marine fuel stabilizer (Amazon Link Ad) to the gas to help with any water that may have gotten in the gas.
10. Bad Spark Plugs
You should change the spark plugs in your jet ski every 50 hours, or once a year.
Bad spark plugs can cause all kinds of running issues, and with how easy they are to change, it’s a no-brainer to do it every year.
11. Blown Engine
A bit on the extreme, but worth saying, a jet ski that won’t reach top speed can be due to a blown engine.
The compression, bearings and a good once over needs to be done on the engine to make sure it’s not blown.
A severely neglected engine can blow, and an engine that was treated right can blow too, but a blown engine will cause a jet ski to not reach its top speed, or even not run at all.
A blown engine should be the last thing on your mind if your jet ski is not getting to its normal top speed, but jet ski engines do blow, so it needs to be mentioned.