Yamaha Outboard Not Pumping Water – Reasons And Solutions

Yamaha Outboard Water Pumping Problems

You bought a second-hand boat. Suddenly a malfunction shows up, that water is not streaming through the motor.

And you are confused about how to fix it.

So, you’re thinking, Why is Yamaha outboard not pumping water?

This type of technical issue occurs in any vehicle and that’s absolutely normal. There might be various reasons behind your outboard not pumping.

Like clogged water stream fitting, the wrong direction of the impeller, the insufficient height of the water, etc.

However, this much information is not sufficient enough. We have got an entire article with 4 reasons and solutions for you to solve this problem.

So, let’s discuss the issue briefly:

Why Is The Yamaha Outboard Not Pumping? – 4 Ways to Repair It

Yamaha Outboard Not Pumping Water

Rather than calling a technician, you can solve any of these problems by yourself. If you have minimum technical knowledge.

We have found 4 problems and given a proper solution to each of them.

These might help even when you have issues with your Yamaha 300 outboard.

Don’t worry, you got our back. We will help you to restore your motor in no time.

Problem 1: Water Stream Fitting is Clogged

There is a chance that your motor’s water stream fitting is clogged. Insects always try to crawl up into the outlet hole.

Most of the time, they get stuck inside the hole and die.

You can find out if there’s dirt or not by moving the motor’s bottom cover. Then look into the water stream fitting.


To clean the clogged area, you need to follow two steps. These will help you to clean the dirt off in the easiest way.

Step 1: Cleaning Dirt

There is a water stream fitting located at the bottom of your motor’s cover. By poking a thin piece of wire, you can clear the fitting. Then pull out any debris or insects.

In the same way, check out the cooling water intakes. Clear them out with a thin wire, if they are clogged as well.

In the meantime, you might be thinking about replacing your Yamaha outboard ignition switch. Just in case, it has been clogged by debris.

Step 2: Keep An Eye on The Lower-Rear Part

You need to connect a garden hose to the motor’s flushing point. Over the raw intake, you have to put the hose.

Turn on the water, start the motor and keep warming it to its usual operating temperature.

Stay alert while it’s heating up your outboard’s top cover.

Caution: You need to follow the safety measures while fixing the motor. Maintaining precautions saves you from any harm. Try to be more cautious while using the wrench. Unless you might get an injury.

Problem 02: Insufficient Water Height

Insufficient Water Height

Insufficient water height could be a reason as well. Less water can’t cover inlets, thus it prevents water from getting to the pump. As a result, it isn’t pumping.

In the summertime, the sun evaporates the water from rivers, canals, and seas. Hence, your motor can’t pump water.


So, you need to place the outboard motor above 60 feet. You can take your boat to a big canal or a river or even to the sea.

Then turn your motor on and check if the motor pumps water or not. This can even create issues with your 4 stroke Yamaha 115.

Problem 03: Telltale Placed to The Wrong Side

Another valid reason is, you are forcing water into the telltale in the back. Hence, the motor is unable to pump water.

If the telltale is misplaced, water can’t flow through the pipe. The motor gets stuck and becomes unable to pump water.


If you have set the telltale in the wrong direction, you need to detach that part. And set it in the forwarding direction.

With the help of a wrench, unplug all the nuts and bolts. Detach the telltale from the motor.

Now take the telltale and put it in the forward direction. Then set all nuts and bolts once again.

By now you have understood what will be the next step.

Exactly, you’re right. Turn the motor on and watch if it’s streaming water or not.

Problem 04: Impeller Is Damaged

If any solution explained above doesn’t work for you, the problem is somewhere else. You have to understand that the impeller is damaged or worn beyond repair.

Thus, it needs a replacement.


Before taking a determined decision about your motor, cross-check the outboard motor once more. This process will help to pick the proper decision.

We have explained the procedure down below-

Step 1: Inspect The Water Stream Fitting Once Again

Again, inspect the water stream fitting. You will get to know the impeller is working if you find water is pouring forth.

But turn off the motor immediately, just after you realize that no stream of water is coming through the motor’s cover.

Now, you have understood that the problem is nowhere but in the impeller.

Step 2:Cut Off the Faulty Impeller

As we have identified the issue, it’s time to replace it with a new one.

Firstly, unscrew nuts and bolts which are attached to the lower unit with a thin-wall socket.

Then, you need to untie the water pump by removing the bolts, using an adjustable wrench. Now, open the pump cover up then place it on the top of the driveshaft.

Just similar to the pump cover, pull out the impeller and place of the driveshaft.

Step 3: Insert A New Impeller

In this step, you will need to change the impeller. There are quite a number of impellers available in the market

Under the water pump’s cover, you have to insert a new gasket in the groove. Later, attach a bead of gasket sealer to the gasket.

Lastly, put back the pump cover and impeller down further. Slowly move the driveshaft onto the pump’s faceplate on the lower unit.

Finally, you’ll have your Yamaha outboard pumping water. In case, it still doesn’t work, contact a professional.

Problem 05: Thermostat Failure

The thermostat regulates the flow of coolant to the engine to maintain a proper operating temperature.

When it fails, the coolant flow is either restricted or completely cut off, which can result in engine overheating and other related problems.


  • The engine starts and runs normally but no water is being pumped through the engine.
  • Overheats quickly.
  • Engine may stall or shut down suddenly.


Ensure that the water intake is free from debris or blockage, as this can restrict or cut off the flow of water to the engine.

Ensure that the water pump is working properly and that the impeller is not damaged or worn.

Remove the thermostat housing and inspect the thermostat for signs of damage or wear.

If the thermostat is stuck in the closed position, it will restrict the flow of coolant to the engine and cause overheating. If it’s damaged, replace it with a new one.

Ensure that all hoses and connections are secure and free from leaks.

Ensure that the engine coolant level is at the proper level and that the mixture is correct for the engine.

Note: If you are unsure about the condition of the thermostat or any other part of the cooling system, it is recommended that you consult a Yamaha outboard dealer or a qualified marine mechanic for further assistance.

If the above steps do not resolve the issue, further troubleshooting may be necessary. It’s important to address this issue promptly to avoid permanent damage to the engine.


Yamaha outboard thermostat faqs

Why is my Yamaha outboard not peeing?

Give a quick check to the thermostat. If it is clogged with salt or has been stuck, try vinegar flush as it removes the blockage.

How could I know if my outboard water pump is bad?

If you find that the outboard motor is overheating, the impeller is living on borrowed time, or there is a reduced stream of water from the cooling water outlet.

Should water coming out of the outboard be hot?

The water will be warm but not super hot. When it’s warm you know the water is pulling heat out of the engine to keep it cool as it should.

Why is my outboard turning over but not starting?

If your outboard is turning over but not starting, it could be due to a variety of reasons. Here are some steps you can follow to troubleshoot the issue:

Fuel system: Ensure that you have enough fuel in the tank, that the fuel line is connected, and that the fuel filter is clean. If the fuel filter is dirty, replace it.

Spark plug: Inspect the spark plug for signs of wear, corrosion, or damage. If the spark plug is fouled or damaged, replace it.

Battery: Ensure that the battery has enough charge to turn over the engine. If the battery is weak, charge it or replace it.

Ignition system: If the starter is working properly, inspect the ignition system for any issues. Check the spark plug wires, the coil, and the ignition switch for signs of wear, corrosion, or damage.

Fuel-to-air mixture: Ensure that the fuel-to-air mixture is correct. If the mixture is too rich or too lean, it can cause the engine to turn over but not start.

Compression: If all of the above steps have been completed and the engine still won’t start, check the compression.

Low compression can cause the engine to turn over but not start.

If you’re still unable to start the engine, it’s recommended that you seek the assistance of a professional outboard mechanic. They can diagnose and repair any issues that may be causing the problem.

Bottom Line

restoring your water pump

We’ve just shown you all the solutions for your Yamaha outboard not pumping water. We are hopeful that you can fix this problem by yourself.

Don’t hesitate to share your experience while restoring your water pump. Encouragement helps us to grow.

So, let’s hope that nothing goes wrong and best of luck.

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