Jet Boat Won’t Start – 10 Things To Try

If you go out to your jet boat and notice it won’t start, don’t panic, it’s usually something simple.

We’ll list all the things that can keep a jet boat from starting so that you can get back on the water and having fun!

1. Check The Battery Switch

I’ve seen many people forget to turn the battery switch to the on position or switch it to the wrong position.

Some battery switches have either an on or off position. Some boats have a 3rd position for dual batteries or deep cycle batteries.

You need to make sure you have the switch turned to the correct setting before starting the boat.

2. Check The Kill Switch

Not only do you have a battery switch, but you also have a kill switch.

The gauges may come on, but when you turn the key to the start position, nothing happens.

Located near the key or the shifter is a place to plug in your kill switch (The red lanyard next to the shifter in the picture above). If it is not plugged in, the engines will never start. If you remove this switch, the engines shut off.

This lanyard is supposed to be connected to you for the just in case you fall out or get flung to one side of the boat.

Don’t feel bad if the reason your jet boat won’t start is because of this. I’ve seen experts forget about this and tear the boat apart to figure out why it doesn’t start. One thing I do so I don’t forget is after detaching the lanyard from myself, I then attach them to my keys, so I don’t lose either and as a reminder.

3. Make Sure You’re In Neutral

A jet boat will not start unless it’s in neutral.

I’ve seen many times what looks like the jet boat is in neutral but come to find out it was slightly forward.

I like to move the lever just a little to make sure I’m locked in neutral first, just like you would for a manual transmission car.

4. Make Sure You Have Gas

Gas tanks on jet boats are quite large, and you’ll need more than a gallon or two to prime the engine. Make sure you have plenty of gas before starting the engine.

Also, don’t forget to run the blower after putting gas in the boat or before starting it!

If the gas is a few months old, then it could be bad gas. You’ll want to put STA-BIL (ad) in the gas if you’re not going to be riding it for a while.

5. Check The Battery On Your Jet Boat

Most of the time, it’s the battery.

If you did not use your jet boat for a few months and did not keep the battery on charge, it’s for sure the battery.

Tip: Get a smart battery charger like this one on Amazon (ad) to keep your battery charged when you’re not using it. If you don’t have a plug where you keep your jet boat, then you can get a solar charger like this one (ad) that will work just as good. I prefer the solar charger as it’s easier to deal with and you don’t need any power outlets.

Just like your car, if you don’t use your jet boat for a few months, the battery dies. The battery dies because nothing is keeping it active, so the plates inside sulfate.

You can sometimes recover a battery by charging it, but most often, it doesn’t last for long. It’s better to get a new battery.

All boats use very similar batteries; this is the kind of boat battery I like to use on Amazon (ad). It’s important to stick to the marine starting batteries due to the abuse from jumping waves and the wet environment that boats go through.

6. Jet Boat Clicks

If you go to start your jet boat and all it does is click once, then you need to replace the starter relay. If it’s a dual-engine jet boat, you may hear two clicks, so long as the clicks are not clicking repeatedly, then it’s the starter relay.

The starter relay is not hard to replace. Most often, all you need is a 10mm wrench and to disconnect the battery before working on it.

The starter relays are brand specific, so the one for a Yamaha Jet Boat won’t always work for the Scarab Jet Boats.

Your local dealer or repair shop should have these in stock. Many will even come out to your dock to replace it as it’s not an involved process, but they will still charge for going out to your home.

7. Jet Boat Clicks Multiple Times

If you try to start your jet boat and all you get is multiple clicking, then that means your battery is too weak to start the engine.

Usually, charging the battery is all you need to do in this case.

The only way to test if a battery is good is with a load tester. You’ll have to take the battery to your local auto parts store and let them test it.

Note: It’s rare but I’ve seen brand new batteries fail. Even if you think the battery is perfect you should still load test it.

I have seen cases where the battery was fine, but the cable was loose on the battery. The water can be rough and loosen the cables on top of the battery.

You’ll want to avoid using wing nuts for your battery and use nuts that you have to tighten with a wrench. If all you have is wing nuts, then use plyers to get them tighter than what your fingers can.

If the boat is old enough, the battery cables themselves could be bad or corroded. This is more of an issue for coastal boats. Corroded cables need to be replaced with new ones as both ends of the cable are usually bad.

8. Battery Is Fine and So Is The Starter Relay

Another possibility to why your jet boat won’t start is because you sucked something up.

The engine is connected directly to the impeller, and if something is keeping the impeller from moving, then the engine won’t move either.

Jet boats don’t have transmissions, but instead, use a bucket to direct the water flow. You can read more about this here.

If you’re trying to start the jet boat in too shallow of water, then it’s a good possibility that you sucked up something like a rock, and that is keeping the engine from firing up.

You’ll want to start the engine in at least 3 feet of water, any lower and you’ll suck up debris.

Yamaha jet boats have a cleanout port, as shown below, but it’s only useful for seaweeds or ropes. If you sucked up rocks or sticks, you’d need to get the jet boat out of the water to remove it. Just makes sure to disconnect the battery before working near the intake of your jet boat!

Also note, the Yamaha cleanout ports often have a switch that keeps the engine from starting. This is to prevent people from opening this port when the engine is running. Make sure those switches are correct, as it could be why the engine won’t start. This switch can have two positions, too, so make sure everything is seated correctly.

9. Check Fuses And Breaker Box

Check the fuses. Sometimes you can have a blown fuse that is keeping the jet boat from starting.

Keep in mind a jet boat can have multiple fuse box locations. You’ll have one for each engine and often a fuse box or breaker box near the driver’s seat or the battery. The picture at the very top of this article shows you a battery with the breaker box next to it.

You may have even more fuses than that, so it’s best to check your owner’s manual for all locations.

10. Check Spark Plugs and Ignition Coils

I’ve seen a few times a guy take his boat in for a service, and the tech forgets to reconnect the ignition coils.

The ignition coils go on top of the spark plugs and often have two wires that click in as one unit. Make sure the ignition coils are properly seated and connected.

If you’re having starting issues where the engine will turn over but won’t fire up or stay running, I would go ahead and replace the spark plugs. It’s a good idea to replace the spark plugs once a year or when you get the engine serviced.

If you winterized the jet boat and fogged the motor, it could merely be the spark plugs are fouled. Fogging the engine can make the spark plugs go bad due to the nature of the fogging protecting the engine.

Jet Boat Still Won’t Start!

If you have gotten this far, then there is nothing simple left to check. You’ll need to take the jet boat in for repairs.

Jet boats are very simple in their design but often have complicated tech. If your jet boat still doesn’t start you’ll need a dealership that can hook it up to the computer to see what is going on.