3 Common Problems With Mercury 4 Stroke Outboard Motor

Mercury four-stroke outboard engines are designed and built innovatively to ensure high-quality performances as well.

Besides being such an amazingly reliable outboard motors, they still have some common troubleshooting issues that most users encounter.

In this very article, I will reveal possible reasons behind each of those common issues and suggest some useful quick-fixing techniques.

Outboard Motor Does Not StartEmpty gas tank or dirty, low-quality fuelClosed gas tank air ventClogged fuel filter or fuel line leakageDamaged batteryFaulty kill switch
Engine May Stalls, Loss Power or Make Excessive VibrationDamaged, loose, or fouled propellerDamaged or broken shear pinWorn-out or damaged spark plugs
Overheating IssueLeakage in the cooling systemleakage in the cooling system

3 Common Mercury 4 Stroke Outboard Motor Problems:

1. Outboard Motor Does Not Start:  

The first common troubleshooting issue that most users complain about is when the mercury four-stroke motor suddenly fails to start like usual. 

In some cases, the engine may crank slowly but still fails to start over. Some users have also claimed that sometimes the motor starts after several tries but quickly starts to stall.

However, to fix the problem, you need to find out the core reason behind this arisen commotion.

Possible Fix 

If you encounter similar commotion with your mercury 4 stroke motor, verify the core issue with the following possible reasons.

Empty gas tank or dirty, low-quality fuel can cause it…

There can be various reasons behind this, but the first and foremost task is to check your gas tank. 

If the fuel level is low or you have a dirty fuel mixture, change and refill the gas tank with the correct fuel mixture. For fuel mixture’s correct ratio, take help from your outboard service manual.

Remember old gasoline gradually harms your engine, so you need to check the fuel level and condition frequently. Also, if you are using ethanol gasoline, do not use fresh refilled gas for more than 30 days in a row.

Another possible reason can be the gas tank’s air vent condition…

Check your gas tank whether the gas tank vent is open or closed. If you see the vent is closed that the main culprit you need to deal with first.

A closed gas tank vent prevents the air from replacing fuel when the motor pulls it out, and as a result, a lack of firing up causes the engine to fail.

Besides checking the gas tank vent also, inspect whether the engine is primed and choked properly. Remember to check whether the fuel shutoff valve is turned on or off.

A clogged fuel filter or leakage on the fuel line can also cause such trouble…

First, you need to disconnect all the connections and remove the fuel filter from the fuel lines. 

If you see debris inside the filter or fuel lines, clean them by spraying solvent cleaner. Next, wait for some time so that the filter or lines get properly dried and re-insert it accurately. 

Remember, if the damage is severe, you will need to replace the filters or fuel lines. Also, check the hoses for any possible leaks and replace the parts, if needed.

Either for damaged battery or a faulty kill switch…

If your mercury 4 stroke is the pull-start outboard motor, you should also inspect the battery whether it is damaged or not charged. Make sure the battery is clean and all the connections are on point. Remember to charge the battery is fully.  

Next, you need to inspect the kill switch connection, and if it is not connected securely, undo the connection and re-install it properly. 

If the kill switch looks damaged, replace it and put the gear on neutral before starting the engine.  

2. Engine May Stalls, Loss Power Or Make Excessive Vibration: 

Another commonly mentioned problem with mercury 4 stroke outboard or boat engines is frequent stalling, sudden loss of power, and excessive noises.

Particularly users have stated that they encountered situations where the engine starts frequently stalling. Sometimes they notice significant power loss and unusual excess vibrating sound coming from the engine too. 

Some users specifically mentioned that it happens when the motor is warm up enough and turns on the idle gear to start.

Therefore, let’s find out what may cause those types of trouble and how to get rid of them.   

Possible Fix 

These problems can arise because of one or more following reasons so, make sure you are investigating all possible faults thoroughly.

A damaged, loose, or fouled propeller can cause the problem…

Whenever you encounter these similar issues with your mercury 4 stroke, instantly turn off the engine and disconnect all the connectors to pull your propeller out. 

Now, check whether something like excessive seaweed or other debris tangled around the propeller or not. 

If you find any tangled materials that can enter the blades to damage them, carefully remove them. Next, clean the entire propeller to remove all the existing debris. 

Also, check the propeller blades if those are not free from breaks, your propeller needs to be replaced. 

The damaged or broken shear pin can also lead the engine to lose power and make excessive vibration or rattling noises.

The shear pin is responsible for directing the propeller to spin with an accurate angle and direction.

But because of the broken or damaged shear pin, the propeller fails to spin and causes the engine to lose power and make unnecessary noises. In that case, you need to replace the shear pin.   

Worn-out or damaged spark plugs can be another possible reason…

First, you need to check the ignition spark with a spark tester. If the spark is good, make sure the air gap in between is according to the   needed specification. 

In case you cannot find the spark, there are two easy ways to deal with spark plugs. One is if those are dirty because of the excess debris, carefully disconnect and remove them. Then, neatly clean and dry off to put them back in place. Another way is if one or all spark plugs are damaged, replace them.

3. Overheating Issue: 

Another most common issue that often mercury four stroke users complain about is the engine or motor overheating problem.

When the outboard motor gets overheated, it abruptly shuts off and won’t start again, which is natural because it needs to cool down first and after that, if you will try, it will re-start. 

Now I will try to explain some most obvious reasons behind this particular problem.

So, let’s learn and explore together.

Possible Fix 

Any leakage in the cooling system can cause overheating trouble…

It is one of the core reasons for outboard motor overheating so, the first and foremost task is to check your cooling system for any possible leak. 

First, check on the radiator, hoses, gasket head, or thermostat housing. If you find any external leak, the temporary solution is using the mercury hose repair kits or sealers instantly. 

Remember to carry extra hoses, hose clamps, and kits for emergency repairing tasks.

However, those are temporary quick solutions, but a better way is to use the permanent solution. The permanent repairing option for you is to replace each leaked part, if possible. This replacement will require a professional assistant so, hire a professional mechanic or contact your mercury outboard dealer.

Another reason can be damaged or worn-out water pump impeller…

Therefore, check the water pump impeller whether it is broken or miss any vane. Thoroughly inspect if there any displaced pieces which are causing the trouble. If so, you need to remove and fix them accurately in place. 

Next, you need to check whether the water passages are clogged with debris or other harmful materials. That clogged passage will prevent the flow to run smoothly so, flush it with clean water and professional cleaner.

What The Majority of Users Feel About the Mercury 4 Stroke Outboard Motor?

After reviewing several consumer’s feedback, there is no doubt that most of the users are more than satisfied with their outboard experiences because of the classic performance and reliability.

However, some users have mentioned their disappointments because of the mentioned troubleshooting issues with the mercury 4 stroke outboard motors.

But the good news is, all the common problems that may arise with the mercury product line are easy to fix, and mercury also ensures the highest after-sale service through its wide range of dealers.

Final Thoughts:

Besides all the common problems with the mercury four-stroke outboard motors, it is undeniable that Mercury Marine is one of the industry leaders for its innovative and technologically advanced outboard motors.

Therefore, you cannot outlook the exceptional power and speed each mercury outboard or boat motors offer.

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