How to Repair a Submerged ATV

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Whether you are stuck with the misfortune of sending your ATV through the ice on a frozen lake or if you’ve sunk it into a bottomless mudhole, there are some crucial steps you need to take to save your bike from the junkyard.

I know exactly how you feel right now, but fear not! The bike is not necessarily trashed; you can most likely salvage it without breaking the bank.

If you are somewhat mechanically inclined, you should have no problems performing this recovery on your own.

If there is no engine damage, your ATV has a good chance of getting back in shape without any permanent damage. All you have to do is to follow the steps in this guide.

Yes, there are a lot of steps, but not all are too time-consuming. Time-wise, you should set aside the better half of a day to do this properly.

If you skip some or parts of the steps, you may pay the consequences later, so take your time to do it properly.

How Water Enters the Engine and Why It Is Bad

Before I get into the steps, I’ll address why water may sometimes enter your engine. It is not only when you sink the bike to the bottom of the ocean this may happen.

If you ride fast through deep water, it may splash up into the air intake, sucking water into the engine. Riders who intentionally ride in waist-deep mud install snorkels to prevent this from happening, but you are not safe even then.

When ample amounts of water enter the engine, it will hydro lock. The amount of water needed for this to happen is surprisingly tiny.

I won’t get too technical as I’m not claiming to be a trained mechanic. Basically, what happens is that when the piston goes up in the cylinder, it compresses the air above the piston just as it is supposed to.

But water cannot be compressed, at least very little, unlike air. So if you get more water inside the cylinder than the volume above the piston, when it is at its highest point (not very much!), the excess water has nowhere to go.

The piston cannot complete its travel. It’s like squeezing 2 liters of water inside a 1-liter bottle. It cannot be done.

When this happens, one of two things will occur:

If you are lucky, all that happens is that the engine stops when the piston cannot travel any further. This is more likely if the hydro lock occurs when the engine is idling or you are not using too much power.

The engine can also die out before any damage is done to the engine if it chokes out because of water entering the air/fuel mixture.

If you are not so lucky, you will get one or more mechanical failures like bent or broken piston rods, fractured crankcase, engine head or engine block, and damaged bearings or valves.

All because the piston tries to neglect the laws of physics. Keep in mind that damage to the engine is more likely when the hydro lock happens at speed.

If you hear any abnormal metal sounds when the water enters, you may be out of luck. You may be able to bring back to life a damaged engine after a substantial rebuild, or in the worst case; you may need to replace the whole engine.

If you have completed this guide, including installing new spark plugs, and the engine still won’t run or runs rough, it’s time to start thinking of calling your favorite mechanic.

A simple compression test may indicate if everything is as it’s supposed to be.

But enough with the what’s and if’s. You have quite a lot of work ahead of you, so let’s start recovering!

1. Get the ATV Out of the Water

As soon as you get water into the engine, hit the kill switch and get a buddy. The bike must get out of the water as quickly as possible to prevent more water from seeping everywhere.

You will need a winch, or a tugboat, depending on how deep of a mess you’ve gotten yourself in.

Turn off the key. Please put it in neutral and tow it on shore.

2. Count to Ten, Take a Deep Breath, and Shake It Off!

At this point, you are your own worst enemy. You are panicking and may be acting irrationally.

Doing the wrong things now will only make the situation worse.

So before you move on, you need to make sure you are thinking clearly. Now is not the time to do anything hasty.

Whatever you do, DO NOT try to start the engine at this point. It is most likely hydro locked, and trying to start it may cause or worsen any damage that already has occurred.

3. Drain the Air Filter Box and Remove the Filter

Your air filter box will likely be full of water at this point. The box must be cleaned to prevent more water or dirt from entering the engine.

  • Remove the seat. Open the airbox and remove the filter. If you have a Honda, also remove the little crankcase filter.
  • Open the airbox drain plug, or remove the whole box if it cannot be drained.
  • Before you reassemble the airbox, later on, you should clean out any water or mud and let it dry.
  • Clean the air filter if it is of the reusable foam type. Ensure it is dry, and apply air filter oil before installing it.
  • If the bike has a paper-type air filter, it will be waterlogged by now and needs replacing.
  • Disassemble the whole airbox and clean out all of the water and mud. If you’ve been riding in mud, you will need a new air filter.

4. Twelve-O’clock the ATV

Get help from a buddy or three and tip the bike 90 degrees backward until water stops running out of the motor and the exhaust. Then set it back down again.

Now you are done with the initial “first-aid” and should get the bike to wherever your tools are.

Tow it, put it on a trailer, or airlift it with a helicopter. But do not ride it at this point!

When you get home, your goal is to get the water out of the engine as soon as possible.

5. Clean the Air Inlet and Breather Tubes

Clean out the air inlet if there is any mud or muck. Ensure no mud is left so you don’t suck any additional debris into the engine when you start it.

Do not forget to clean the breather tubes. Disassemble them, rinse them in water, and let them dry before you reassemble them.

6. Dry Out the Stator

Water may have entered the stator housing depending on how long your bike was submerged. Remove the stator cover, and some water will likely pour out.

Using an air compressor with an air nozzle, blow from all angles to get most of the water out. Then use a hairdryer or heat gun to dry out the rest of the moisture. Be careful not to melt anything or set the ATV on fire.

If you don’t have these tools, you must wait longer for the stator to dry out. But make sure the stator housing is completely dry before reinstalling the cover.

7. Dry Out the CVT Belt Housing

If your bike has a belt-driven transmission, you must drain all the water. Most bikes have a drain plug at the bottom that you can open. If your bike doesn’t have this, you must open the belt housing cover.

If you were riding in muddy water, you should preferably open the cover to clean the inside and the pulleys. Let dry before you reassemble. If you ride with a wet belt, you may get belt burning.

8. Flush the Cooling System

If your bike was submerged entirely, you must flush the cooling system to remove any contaminated water. Water may have entered through the overflow.

Drain it. Run it with clean water for some minutes. Drain again and fill up with the factory-spec coolant.

9. Drain the Gas Tank and Carburetor

Again, if the bike was completely submerged, you will likely have gotten water inside your gas tank. Drain the tank and the carburetor on a carbureted ATV or the throttle body, which holds the injector on a fuel-injected machine.

If you are lucky, you will find a small screw at the very bottom of each of these components for easy draining. If not, you have to be creative.

If the carburetor does not have a drain screw, you can drop the float bowl (the bottom part, held in place with four screws).

Also, disconnect the throttle body/carb air duct inlet tube and dry it out.

If your bike has a carburetor and you want to do an extra thorough job, you should consider cleaning the carburetor insides to ensure you get rid of any remaining moisture or dirt.

Take the carburetor out of the bike and disassemble it. You can leave the floater in place, but it’s best to remove the jets for better access.

Use compressed air to blow in any hole and angle to get as much of the water out. Spray it with carb cleaner. Then let it dry completely before reassembling it.

If the bike was submerged for some time, the gaskets may be soaked in water and need drying or replacing. They are only a few bucks, so a re-pack is recommended.

With the carb off, use a paper towel to clean the intake manifold and the reed valve area (outlet). Then reassemble the carb and install it to the ATV.

10. Remove Water Trapped Inside the Cylinders

Now it’s time to start the engine to blow out any remaining water from the engine. You must also lube it to prevent the engine’s internals from rusting.

Remove all spark plug wires and spark plugs (or the injectors if the bike is fuel-injected). This creates an opening for the water and pressure to escape when the cylinder moves.

Do not skip this part because failing to create an opening at the top of each cylinder will possibly lead to hydro-locking and damage to the engine! Consider yourself warned.

Turn the engine several times until it stops squirting water from the spark plugs or injector holes. Use the kick starter if the bike does not have a starter. A good 5 minutes of kicking should do the job.

Put everything back in place and start the four-wheeler. Don’t rev it. Let it idle for some minutes to let it clear the exhaust.

While it runs, spray some WD40 into the air inlet to lube up the motor’s insides and displace any water. Some prefer Seafoam, but be aware it may gum up your carburetor.

If you spray too much, you will choke out the motor, so spray just short bursts until you have gotten a general amount of lube inside the engine.

It will smoke like crazy because of the water evaporating and the wd 40 burning but don’t be alarmed; this is normal, at least for the first couple of minutes.

11. Replace the Plugs

If your bike has plugs, they were likely fouled when it hit the water and need replacing before you can start the engine.

Then it may start and run for some seconds before it dies again.

Expect to go through about 3-4 plugs before you get the bike going. A minimal amount of water left in the engine will be enough to foul the plug when initially trying to start it.

Be patient, and check for a spark. Using starter fluid or trying to jump-start the bike is not recommended, as this will only result in more fouled plugs.

If the bike runs rough, try replacing the spark plugs, as they have likely gone bad.

12. Change the Engine Oil

You may have been lucky and avoided getting water into the engine oil, but it’s not worth risking it if you are unsure. By pulling the dipstick, you may see if water is mixed with the oil.

You will get a definite answer as soon as you drain the crankcase. If the oil got water into it will not look black (or clear brown if it was new). It will look light brown and mushy, almost like creamy coffee.

After draining the contaminated oil, fill up with ordinary diesel to flush out any bad oil and water. Because of the diesel’s limited lubing abilities, you should not ride the bike or rev it with diesel in the engine.

Don’t install a new filter yet; it will need replacing anyway. Just put the cover back on with no filter. If the bike has a can-style filter and cannot be started without a filter installed, use a cheap one.

Start the engine and let it idle for a couple of minutes. Stop the bike and drain the diesel. Repeat one more time or until you see only clear diesel.

The final time, let it drain for 30 minutes to get most of the diesel out.

Then you should add cheap engine oil to the maximum mark on the dipstick. You can skip diesel altogether, but this means using more oil which costs more.

Start the bike and let it idle for 10 minutes to allow the oil to mix with any remaining water or diesel. Drain and repeat one more time.

After draining the second time, you can install a new filter and quality oil according to factory specs.

Now you are done!

13. Check Differentials and Transmission for Water

Start by opening the cap where you would typically fill the oil. Stick your little finger in and dip it in the oil. If the oil is clear, you are OK and can move on to the next step.

If it is creamy white, like the engine oil, water got in and needs replacing.

Drain all of the oil. You may need to tilt the bike to both sides to get it all out. If you have access to an air compressor, you will get more oil out by blowing air into the filler hole.

Fill up with some cheap oil as you did with the engine. Ride the bike for some minutes and immediately drain out the oil again. Repeat until the oil looks clear.

Then fill up with the manufacturer-specific oil according to the specs in the manual (usually until the oil runs out of the overflow/fill hole with the bike on a level surface).

14. Flush the Brakes

Really? Arent the brakes a sealed system, you may ask. How can water get in?

Well, the reservoir at the master cylinder will have a vented cap that allows air to enter or escape any time the cylinder is depressed or released. And if this cap ends up below water, water will enter the brake system.

Get some new brake fluid that matches your user manual’s requirements (usually DOT3/4). Start flushing the system by bleeding the brakes while you regularly top off with fresh brake fluid.

DO NOT let the reservoir tank level drop below the minimum mark, as air may enter the system, and the job will take much longer than necessary.

15. Dry and Lube Electric Connections

This step is primarily to prevent any issues down the road.

Disconnect all accessible electrical connections and inline fuses and blow them out. Give them a shot of WD40 before you reconnect them.

This will prevent any corrosion and bad connections later on.

16 Grease the ATV

Simply because it deserves it; after all, you’ve put it through! This will also prevent rust.

Haavard Krislok
Haavard Krislok
Haavard Krislok is an ATV and off-road enthusiast with a rich background spanning two decades in owning, maintaining, repairing, and utilizing ATVs for farming, logging, and hunting. Outside his professional life as an engineer and project manager, he cherishes recreational trail riding and is the creative force behind, serving as its owner, editor, and content creator.

Welcome to Boost ATV

Hi, I’m Haavard, the guy behind Boost ATV.  I made this site to share what I have learned as an avid ATV owner and enthusiast. I hope it can help boost your ATV experience! About Me