Rev Up Your Engines: Testing Your Boat Motor Out of Water!

How to Test a Boat Motor Out of Water

Ahoy there, mateys! I’m Bill, and I’m here to talk about one of the most crucial routine maintenance tasks for all you boat owners out there – flushing your motor!

Now, I know what you’re thinking, “Bill, that sounds about as exciting as watching paint dry.” But trust me, this is no walk in the park.

First things first, let’s get one thing straight. You never, and I mean NEVER, want to run your boat’s engine without water. That’s like trying to survive on a deserted island with no water – it’s just not gonna happen. So, grab your hose and attach it to the water intakes, pronto!

Now, if you’re one of the lucky few, your motor might have a built-in attachment that accepts a hose nozzle.

But if it doesn’t, fear not! You can always use some fancy motor flusher muffs to get the job done. Just make sure those bad boys are securely in place before you turn on the water.

Speaking of turning on the water, don’t forget to run it before you start the engine. Otherwise, you might end up with some major engine damage on your hands. And let’s face it, nobody wants to deal with that kind of headache.

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Once you’ve got the water running, it’s time to fire up that engine and let it run for a good five to ten minutes. But, don’t just take my word for it. Check the user manual to see what the engine’s manufacturer recommends. After all, they’re the experts here.

So, there you have it, folks. Flushing your motor might not be the most glamorous task, but it’s one of the most important. Plus, you’ll feel like a true boat captain once you’ve completed it like a pro. Now, who’s ready to hit the high seas!?

3 Steps to Test a Boat Motor Out of Water


Step 1: Hooking the hose and the flusher muffs

i. Go through the manual

Before you start the motor out of the water, go through the manual.

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It will tell you where the intakes are and inform you if they have an attachment for a hose. In case it doesn’t have the attachment, then you will have to use motor muffs.

The flushing recommendations that most manufacturers issue are similar, however, checking what your engine’s manufacturer says precisely helps you follow the most effective procedure.

ii. Hook the hose to the motor

Your motor has the attachment? Great.

Look for the water intakes on the engine’s lower sides, and hook the hose into one of them.

In most cases, the manual recommends that you use heavy tape to cover the other intake.

iii. Get some motor muffs

You’re only going to need some if your engine doesn’t have an attachment for the hose.

You can get these for around 10 dollars online or at a boating store.

iv. Connect the muffs

Some people like wetting the muffs’ insides before connecting them to the motor, as that gives them a better grip and prevents them from coming off when the engine runs.

While clamping the muffs to the motor, ensure they are positioned such that the connecting rod is situated opposite the propeller and in front of the motor.

v. Hook the garden hose to the muffs

One muff is solid, while the other one has a nozzle. Screw the hose onto the one that has a nozzle, making sure the connection is tight.

Step 2: start the engine

i. Turn on the water

As soon as there’s a good connection between the engine and the hose, run the water.

You can refer to the user manual for any water pressure setting specifications. In most case, around half pressure applies. Caution: don’t attempt starting the engine before running the water.

ii. Turn the engine to neutral

Before starting the engine, be sure to put the throttle or gearshift in the neutral position.

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If you’re testing the propeller’s function, you can put the engine in the gear position but first, make sure there are no people or things near the propeller.

iii. Start the engine

Some engines have a starter that you have to pull while others can be started with a key turn; there are yet others where you have to push a button.

iv. Check to ensure the water pump is working properly 

There should be an overflow of water from the upper part of the motor, and if you can’t see it, then something is wrong with the pump.

So, if you can’t see the overflow, switch off the engine.

Maybe there’s some debris blocking the outflow tube – insert a wire in there to confirm this, and if there’s some indeed, remove it.

If after removing the debris, there is still no stream of water from the tube, you probably need to have the pump replaced.

Step 3: Flush the motor

i. Let the engine run 

If the water pump is fine and you can see the overflow, let the engine run for around 10 minutes or as specified in the manual.

If your purpose for running the engine is to flush the motor, then running the engine for five to ten minutes will be enough, but if you want to test another function, you might need to run it for longer.

While the engine is running, keep watch on the muffs, ensuring they’re not coming off.

ii. Turn off the engine 

Once you’re done testing the engine’s function or flushing it, be sure to turn off the engine before you turn off the water.

Remember, having the engine run without water is exposing it to damage.

iii. Detach the hose 

Once you have turned off the engine and the water, detach the hose from the built-in attachment or the muffs.

And after removing the hose, coil it up and store it away. Also, take off the muffs by sliding them off the lower unit of the motor and store them away.

Now, before you tilt the engine, keep it down for an hour or so, to allow the water to drain from the powerhead, and once it has drained, return the motor to the tilted position. And lastly, store the boat as you prefer.

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Another Method for Testing the Motor Out of Water

Follow the following steps to test the motor the easy way:

1. Mount the motor to a firm platform and position a huge water bucket beneath it. Ensure the propeller is totally submerged.

2. Rid the gas can of the old oil-gas mixture, as that might be contaminated.

Then, add the recommended (refer to the user manual) amount of fresh 2-stroke oil and gas into the can. Be sure to use some good-quality oil and gas.

3. So, the motor has not been started in a long time? In that case, some starting fluid will be very helpful.

Disconnect the spark plugs’ rubber shields and remove the plugs so that you can spray the starting fluid into the cavity and the air filter.

4. Use a 12V deep cycle battery to start a problematic motor. In the event that the motor does not start when you pull the cord, you can start it the way you jump a car, using a 12 V battery. Attach the jumper cables to those metal screws at the motor’s starter.


1. How much does rebuilding a boat engine cost?

It will cost you approximately $2500, but of course, the actual cost depends on the specific elements involved.

Purchasing a regular rebuilt midsized outboard motor will probably cost you about $4000 depending on where you buy it from.

If you’re on a budget, consider getting it from a discount dealer rather than a full-service dealer.

Read our guide on pontoon boat cost to get better idea about boat engine price.

2. How do I know that my boat’s water pump is bad?

If there’s no overflow of water at the upper part, then you know there’s something wrong with the pump.

But, before you head to the shop to buy another one, check if the outflow tube is blocked by debris or other material.

3. How does an impeller differ from a propeller?

Both apparatuses offer your boat thrust, but they do it differently.

An impeller is basically a rotor and a part of the pump that creates a sucking force.

A propeller, on the other hand, is a fan that has rotational motion, which it converts into linear motion; it pushes against fluids through its rotational motion.

My Final Thoughts On How to Test a Boat Motor

I hope this guide helped you test the motor out of the seawater.

The most important point to keep in mind is that the engine should never be run without water, as that would damage it.

Also, don’t forget to check the manufacturer’s recommendations on the process.

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