Mercury 9.9 Four Stroke Problems

The mercury 9.9 four strokes are one of the efficient motors for boats, skiffs, small pontoons, and subordinate power sailboats, but you may encounter mercury 9.9 stroke problems. 

Yes, you may face some of the issue’s in mercury 9.9 stroke. But no worries, trouble in starting the engine or engine dies immediately after the running might have different reasons like gunge in the mechanism, fuel not reaching the Carburetor, and many more. Although you don’t need to be a mechanic or throw a massive amount of money to solve these Mercury 9.9 four-stroke problems, you must know the easy ways to fix these problems. 

So, in this article, we have listed one of the most wanted solutions to the mercury 9.9 four stroke problems. Keep reading to know more. 

Mercury 9.9 Four Stroke Problems: In-Depth Explanation 

If you face problems, you must start checking from the primary and easy steps. There are many solutions and tricks to solve the mercury 9.9 four-stroke problems without any expert or throwing many on company services. 

Trouble in Running the Engines

First and foremost, starting from the primary step will save you time and money. 

It starts checking the fuel tap. If anything is stuck, it may cause a problem running the engine, or you may also check the stop switch. If it’s not correctly pulled out, it may shut the machine so the engine doesn’t start. 

The fuel tank must have a 1 liter or half-full tank to proceed to start the engine. You must check if the tank if the fuel tank has efficient petrol init. 

mercury 9.9 four stroke problems
  • Save

The open airway is also one of the most common mistakes sailers make if the engine is dying or shutting without any reason due to the airway being closed. 

The gear should remain in neutral mode, or it will not allow the engine to start and die eventually. You must check before starting the engine. 

Check the fuel pipe connection is tight and not loose or appropriately plugged. It may allow air to go inside and prevent the engine from starting. However, you must change the connector if it’s loose or doesn’t fit properly. 

You must check these things before starting the engines.  

The Carburetor Isn’t Working Properly

The Carburetor doesn’t work if the fuel tank doesn’t pass the petrol appropriately. 

Firstly, check the drain screw bottom of the Carburetor. Take a cloth or plastic sheet, place underneath and unscrew it. If the Carburetor is dry, this may cause trouble starting the engine. 

Secondly, you have to remove the fuel pipe from the socket to check whether the tube is passing the fuel or not. 

You need to pull the core to start the engine and watch if the fuel tank gives the petrol. Suppose it comes out from the pipe. That means no blockage in the line. But if it doesn’t, there is a blockage in the pipe. 

In addition, you may also connect the external fuel tank by pumping the primer to check if the petrol is reaching the Carburetor or not. 

Need a Fix on the Fuel Pump and Filter

In some cases, the fuel filter and fuel pump are blocked because of the gunge. And this may cause the problem. If it’s jammed, you need to insert the new fuel pump by carefully removing the water lines and gas lines. And for the fuel filter, you must find the same size to change it. 

The Spark Plug Might Not be Operating 

Located the spark plug, pulled out the wires, and unscrewed the spark plug. If the color of the spark plug is terrible or black, it means that you have located the problem. 

Before installing the spark plug, check if it’s the same size as the old one. Plus, you must apply grease to the threads to avoid seizing a motor and a small amount on the bottom of the spark plug to have a good electrical connection. 

Now, put it back and use your hand to screw it to put it in its socket, then use the tool to provide pressure to fit in its place perfectly. Insert the wires to their places again, and it’s good to go. 

The Engine Oil Might be Creating the Problem

Turn up the engine so that oil comes out effortlessly. To change the engine oil, you must pull out the oil plug. Also, use a basket to catch the oil. 

Set the motor. By adjusting the lever, turn it from the engine to the oil plug side so that oil comes out easily. then take the nut out from it, and pour the oil until it is empty. After that, you may plug the nut into its place. Mercury oils are very thick so leave it for a while.

After it’s empty, you may put the seal back in its place and straighten the motor before pouring the fresh oil.

Open the upper part of the Mercury, and unscrew the cap. Clean it before putting it back in. put the oil according to the given instructions, and don’t over-filled it. 


  • How Much Mercury Do 9.9 Strokes Consume Fuel?

Mercury 9.9 four strokes is supposed to have a light 14′ Lone star aluminum boat or utility boat and predict the top speed of about 20mph. Mercury four-strokes has 9.9 horsepower and would recommend an 8.5 to 9.5 pitch prop. 

  • How to Change the Fuel Tubes?

You need to lose the hose clamp from both sides of the fuel lines and change it with the new fuel tubes. Make sure it must be tight and should fit perfectly to the motor. 

  • What is the Cause of the Fuel Line Leak?

The reason might be deterioration, connection with something sharp, or rubbing against the gas lines for a long time may cause leakage in the fuel tubes. It’s better to change the fuel lines as soon as possible after finding the leakage. 


Mercury Outboard Bad Coil Symptoms

Mercury Vs. Yamaha Outboard Reliability

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top
Share via
Copy link
Powered by Social Snap