The other day we took out our Sea-doo GTi for some fun with the family wake-boarding and tubing. On one of the trips out we found that there was no acceleration on the Jetski and a lot of cavitation.
So we crawled back to the shore and tilted the Jet-ski on its side to figure out the problem. Surprise! there was a small rock jammed into the impellor.
What causes cavitation on a jet ski
When diagnosing a Sea-doo or Yamaha jet ski cavitation issue always look inside the intake grate and at the rear of the impeller jet. 9 times out of 10 there will be an object stuck in there.
Possible items that can casue cavitiation and acceleration problems are:
- Ski Rope
- Fishing line
- Worn carbon seal (Sea-Doo)
Once you have removed the offending object listed above then you will be good to go fast again.
How to fix Jet ski acceleration problem.
Removing a foreign object is an easy fix. Make sure that it is not left in there too long otherwise you will get jet pump seal wear. Have a look at your impeller seal, it has deep groves more than 2mm then you will need to get it replaced.
If a rock or stick is left jammed between the impellor jet and the seal you will get wear. This wear causes loss of pump pressure and cavitation, thus loss of speed.
You can feel and sometimes hear the cavitation as it will vibrate bad and you won’t move very vast. As soon as you feel and cavitation you must get the Jet-ski onto land or the trailer for inspection. These groves will cause cavitation and loss of jet pump pressure.
Tools needed to fix objects jammed in the impeller jet.
I always carry the following basic tools and equipment while out in my Sea-doo jet-ski.
- Socket set
- Sharp long knife
- long poking stick like a carbon tent rod.
- Anchor for Jet-ski and 30m of rope
- Ground tarp
- DIY metal Impellor jam poking tool.
Put the Jet-ski onto the trailer or lay it on its side on the beach. Use a torch to see where the blockage is at. Use a poking stick to clear the blockage. If it is further down or jammed you will need to take the intake grate off.
Remove the bolts off the intake grate and prise it off. On the assumption that the grate has never been off before it may be stuck on with some factory silicone. Break this seal and you will now have access to the foreign object.
Replace the intage grate and bolt it back up.
If you are out in the water and unable to get to land you can either swim under the jetski or flip the jet ski upside down to look into the intake grate. Make sure the engine is off in both cases.
If you have rope wrapped around the impeller you will have to cut it out. Never leave something wrapped around the impellor as it can case hull damage and or drive shaft warping.
I have used a long knife to slowly cut away at the ski rope that was wrapped around a mates Yamaha wave runner. Just take small cuts along the rope on the shaft, it will slowly come apart.
Any objects stuck in the intake grate are definitely going to cause a Jet Ski acceleration problem. You must stop your engine fast to identify the issue you can minimize any further damage.
How to make an Impellor Jam removal tool.
I now carry a metal rod that has been bent on both ends like the video below. It saves me having to find a stick or take off the intake grate. If you get some thin aluminum rod from your local hardware store it won’t rust over time.
Measure the distance from the intake grate to the impellor. Bend the Impellor jam removal tool to fit. I like the idea of having a hook on one end to help remove rocks and ski ropes.
I just keep it in the front storage compartment of the Sea-Doo.
Spark Plug Problems
I have had one instance of my 4tech Sea-doo engine misfiring. This was at the end of the season before the full Sea-Doo oil change service was due. After a quick pitstop to shore to diagnose the problem we found that one of the spark plug wells was full of oil.
A leaking engine rocker cover o-ring was the cause of the misfiring. To temporarily fix this problem the spark plug coil was removed and cleaned. The spark plug was left in connected to the head and a rag was pushed down to soak up the oil. Problem solved. Hopefully, this helps someone else.
If your Jet-ski tips over and your rocker cover seals are bad, oil can leak into the spark plug area. This is a common problem. Get them replaced.
Water in the spark plugs
If you get water into the spark plug area it could be because they are not sealed up very well. Here is the correct procedure to replace the spark plugs on a Sea-Doo Jet-ski.
Be sure to fully clean and dry the sparkplug coil and plug. Make sure to use Dow Corning No. 4 Electrical Insulating Compound. This will keep the moisture out of the plugs.
Clogged Fuel Injection
Sometimes if your jet ski has been sitting for a few seasons without the engine being run you could have a fuel issue. After a few months you should start the engine so that you don’t get a blocked fuel injector.
One easy fix is to put Stabil fuel stabilizer into your fuel tank after every season before storage. Once out of storage run an injector cleaner through every 5 tanks of fuel. This will keep those fuel injectors nice and clean.
Hopefully, you can quickly rectify your jet ski acceleration problem and get back on the water. There is nothing worse than getting out on the water only to have an issue with your PWC.
I have listed 10 Common Jet Ski Problems and Their Fixes in another article which should help you diagnose other problems. So check that one out for great tips and tricks.
Let me know in the comments below what else you have found stuck up in your intake grate.