A jet boat can be run out of the water for a maximum of 30 seconds.
I repeat, 30 seconds MAX!
There are several reasons why you don’t want to run your jet boat out of the water for too long. Let’s go over those reasons.
A Jet Boat Can Overheat If It’s Not in the Water
Every jet boat takes in water to cool something.
There exist some jet boats that have closed-loop cooling systems like Sea-Doo and Scarab jet boats, but they still take in water to cool certain things like the exhaust.
Yamaha jet boats completely use water to cool everything along with the old school jet boats.
This means if a jet boat is not getting water, the engine is not being cooled. An engine that is overheating is being destroyed along with anything connected to it. Plastic parts start to melt, and electrical connections and bolts begin to loosen up beyond where they need to be. Not only this but metal parts start to weld together, this is not good.
Most boats will have alarms going off when the boat overheats, with some even shutting the engine down. Once you’re getting to the point of alarms, you need to shut the engine off now and let it cool down.
You should not be using the alarms as your cue to turn the engine off. You should also not be walking away from a running jet boat when it’s not in the water.
Starting a jet boat out of the water is more or less a way to make sure things are working correctly before heading to the water. Extreme caution must be considered because when the jet boat engine is on, it means the impeller is spinning. If anything is near the intake of a jet boat, it runs the risk of being sucked up. This is why you must check under and around the boat to make sure nothing is in the way.
If you do get under a jet boat, make sure the wheels are chalked off and disconnect the battery.
The Pump and Bearings
When a jet boat is not in the water, the pump and bearings are not being cooled and lubricated.
You may notice that the jet boat’s pump is much louder and sounds like a bunch of coins raddling in a metal can when out of the water. This is your bearings making all this noise.
The pump and bearings are meant to “float” so there is a good bit of tolerance in the connections. If they’re not in the water, they’re not floating, so they get trashed around in the air.
With the bearings jumping around without the support of the water they wear out quicker. This is another reason not to run your jet boat out of the water for too long.
You also have specific fittings that need to be wet to work correctly.
The Proper Channels Are Not Getting Water
You can flush a jet boat just like any other boat; we’ll talk more about that below.
While flushing is fine, it’s a different intake then where your boat naturally gets water.
The jet pump not only moves you forward but is also the water pump that is used to cool the engine.
The jet pump has a small hole in the housing next to the impeller that is made to siphon water in and pump it through the compartments that need outside water.
Where the flushing port enters is not the same as this intake. I’ve seen several cases where a jet boat will run fine on the hose but not when in the water. It’s because the water intakes are different and you need to keep this in mind.
Running your jet boat on the hose is not a substitute for not taking it to the water. This is something huge to keep in mind if you’re looking to buy a used jet boat. Don’t let a seller trick you into running the boat on the water hose instead of taking it out on the water.
Can You Flush a Jet Boat?
Yes, jet boats have flush adaptors to allow you to flush them.
The most common hook up is fitted to allow you to screw in a water hose.
Some jet boats need a special fitting to work with a garden hose. I know Scarab and Sea-Doo jet boats often are fitted for a garden hose while Yamaha needs the adaptors.
How To Flush A Jet Boat
The way you flush a jet boat is very different than a regular boat.
I repeat, flushing a jet boat IS VERY DIFFERENT THEN A NORMAL BOAT!
This is important to get right, so if you’re in doubt, consult your owners manual.
Flushing a jet boat is similar to a jet ski.
The engine must be on first before you turn on the water hose.
When done flushing, you must turn OFF the water hose before turning the engine off.
The reason you turn off the water before the engine is that a running engine has enough back pressure to keep the water from coming into the wrong ports. A water hose has pressure, and if the engine is off, the water will find it’s way into the cylinders and hydro lock your engine.
So it’s essential that you have the engine on before turning on the water. Then turn the water off before turning the engine off.
If you did it wrong and think you’ve hydro locked your engine, you need to avoid turning the engine on. Get the jet boat to the nearest repair shop so they can remove the water.
The Fear Of Flushing a Jet Boat
I’ve noticed that some people get a fear of flushing their jet boat.
So long as you do the correct order in your owner’s manual, you’ll be fine. I like being over cautious as I’ve seen a few people screw this up, not everyone messes this up, but I must speak up for the few that will.
If you’re afraid to flush your jet boat, I have an easy tip. Most people only flush their boats after taking it to saltwater. The easy way to flush out the salt is to go to a freshwater lake and take it for a 5-minute drive. That’s it.
The other reason to flush your jet boat is when you’re winterizing it. You flush it with Pink RV Anti-freeze, but that deserves its own article.