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How to Start an Inboard Boat Engine Out of Water in 5 Easy Steps

Fact checked by William Hart

how to start an inboard boat engine out of water

There are multiple occasions that require starting a boat motor out of the water, such as warming it up during winterization, checking the vessel before launching on water, or simply doing a regular engine examination. Running a boat on land is not something you can take lightly as the wrong techniques can dry out the engine and cause irreversible damage.

No pressure! All you need to do is constantly supply water into the engine while it’s running. A garden hose and a motor flusher can be used to fake a lake’s water conditions.

Dive in for a step-by-step guide on how to start an inboard boat engine out of water, along with pro tips to keep the engine out of harm’s way while doing this.

Table of Contents

What You Will Need


To be clear, we are providing information on starting an inboard engine, not an outboard one. As said in the name, an inboard motor is mounted inside the vessel, usually at the hull area. Meanwhile, an outboard motor is installed outside the vessel, typically at the back.

Nowadays, outboard engines are more popular due to their increased power control, lower risks of fire hazards, and more affordable prices. If you own an outboard motor, the procedure to start it out of water is different. Kindly check before proceeding.

An inboard motor flusher

An outboard motor flusher looks like an earmuff. One side is connected to the water supply, then to the boat intake hole and pumps water into the engine. The other side is attached to the engine’s inlet vents and sucks water out. Don’t mistake it as an inboard engine flusher.

An inboard engine flusher is sometimes called a circular plunger. Basically, it looks like a toilet plunger and has the same operating principle. The outlet attachment will allow the flusher to connect with a garden hose. The plunger will cover the water intake hole on your vessel, assuring water gets into the motor. Once started, the constant supplies of water will run through the vessel engine.

You can easily buy one at your local Walmart or on Amazon. Every boat owner needs a motor flusher. Besides helping start a boat out of the water, a motor flusher will assist in regular engine cleaning.

A garden hose

You will need a garden hose to supply water. Any garden hose will work as long as it fits the outlet attachment of the flusher. Also, check for leaks on the hose, making sure it works properly.

Steps to Run an Inboard Boat Out of Water


Please be aware that running a boat engine out of water without any source of water supplies can be fatal to the impeller. The cooling system needs running water to lubricate and cool down the engine. It only takes ten seconds of the motor’s running on dry land to damage it severely.

If something goes wrong with the water supply when the motor is running, turn the ignition off as soon as possible. Under ten seconds or so, the impeller has a bigger chance to survive.

After that, move your vessel back on the water and start the engine to see if it runs smoothly. There should be no alarm or red blink on the monitor board. When anything appears to be out of the ordinary, immediately turn the engine off and ask for professional help.

No worries though! As long as you pay close attention while working and turn off the engine in time, no damage will be caused. With that said, start off by parking your boat in a flat, open area, and mounting it on the trailer. Remember that water will be pumped out of the vessel engine; don’t try to run an inboard boat out of water in your garage.

Step 1: Attach the motor flusher to the garden hose

Connect the garden hose to the outlet attachment. Ensure the hose is tight enough to withstand the high pressure of water. Turn the water on to check if there are leaks.

Step 2: Determine where the engine gets water

You need to locate the vessel water intake. Go underneath and you shall see it near the boat motor. Otherwise, check the manual instructions.

Step 3: Set up the plunger

Cover the intake hole with the muff plunger. Then, set up the plunger leg. Adjust the leg height as needed and secure it firmly against the ground. The water hole must be covered entirely and the muff must cling on tightly so it won’t slide when high water pressure is established.

Step 4: Pump water to the engine while the boat motor is running

Turn on the water supply and you should see water pouring down the flusher. Now that all is set, it’s safe to start the engine. Leave the engine on for four to five minutes to make sure it works perfectly. Also, this will help flush out the debris and residues that might have accumulated during winterization.

While the engine is running, keep an eye on the muff plunger to ensure it doesn’t fall off. Water should constantly exit through the exhaust. In addition, you should check the temperature gauge. If the temperature goes over 200 Fahrenheit at any point, immediately switch off the ignition.

Step 5: Turn off the engine

When you are done, turn off the engine. Then, switch off the water supply. Don’t leave the engine running without water. Finally, remove the flusher and disconnect the garden hose. Let it air dry completely and store it for further use.


Boating season is exciting, isn’t it? But you should never launch your boat on the water right after a long storage period. Take action in advance to know if the engine is still working properly. When it is on water and the engine encounters problems, you will need professional help to move the boat back to dry land. Plus, starting an inboard engine out of water would not take much time and effort once you get used to the procedure.

I hope you like this article on how to start an inboard boat engine out of water. Please let me know if you want me to add any more information. And if you need to maintain your boat engine, you can check our list of marine grease and marine fuel stabilizers for easier maintenance.

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