Mercury outboard motors are made with durability in mind.
But irrespective of this, you will encounter some problems some times.
Some of mercury 40 HP 4 stroke problems include overheating, outboard motor not starting, propeller damage, vibration while driving, flooded engine and low performance.
Some are always due to an improper use of your outboard motor.
In this guide, you will learn of mercury 4 stroke 40 hp problems you may likely encounter and how to solve them.
Mercury 4 Stroke 40hp Problems And Its Causes
1) Engine Not Starting
Running into an engine not starting is always a very unpleasant experience.
When it comes to the use of your mercury 40 hp that is 4 stroke, you may encounter this at some point.
When this occurs, your outboard motor will not start when you want it to.
When this occurs, you have to run a troubleshooting to know what really is the cause of this issue.
a) No Fuel In Tank
For your outboard motor to start, there are some things that have to be in place.
One of these things is that fuel has to be present in the tank.
Without this, there will be no fuel for combustion in the combustion chamber.
Due to this, your mercury 40 hp will not start.
So when you run into a situation in which your outboard motor refuses to start, one of the things to check is the volume of fuel in the tank.
b) Flooded Engine
The combustion chamber needs fuel to function.
But not in excess volume.
When the fuel in the combustion chamber is more than what can be burnt, there will be issues.
Excess fuel in the combustion chamber leads to a situation called flooded engine.
When this occurs, then your outboard motor will not be able to start.
This is one of the mercury 4 stroke 40 hp problems some users encounter.
c) Bad Spark Plug
For combustion to take place, a spark has to be delivered to help burn the fuel in the combustion chamber.
This charge is delivered to the combustion chamber with the help of the spark plug.
When the spark plug is bad, this will not be possible.
Due to this, the outboard motor will not be able to start.
d) Bad Stator/Induction coil
In most cases, the spark plug in the outboard motor might be in a good condition but still be unable to deliver adequate electric charge.
When this occurs, you have to check out for the working condition of the charge producers.
This has to do with the stator and the ignition coil.
If they go bad, then the charge needed for combustion will not be delivered.
This is because components like the ignition coil help to super charge the electric charge it receives before sending it to the spark plug.
When a component like this gets faulty, then combustion will not be able to take place.
Due to this, the outboard motor will not be able to start.
a) Supply Fuel To Tank
If you discover that there is no fuel in your outboard motor tank, you have to make sure that you supply fuel into the tank.
This will help your mercury 40 hp outboard motor to start.
b) Allow Excess Fuel In Combustion Chamber To Dry
Fuel is needed in the combustion chamber before combustion can take place.
But an excess of it is as worse as not having any at all.
An excess fuel in the combustion chamber will easily lead to a flooded engine situation.
This will prevent the outboard motor from starting.
To correct this, you have to give some time for the excess fuel to dry before starting again.
c) Use Good Spark Plug
Always make sure that you use a good spark plug in your outboard motor.
This will help deliver the needed electric charges to the combustion chamber.
If you discover that your spark plugs are bad, you have to make sure that you change it to a good one.
d) Use Good Stator/Induction Coil
For an effective combustion to take place, the combustion chamber has to receive an optimum charge.
But how can this be possible if the charge producers like the stator or the ignition coil are not functioning well.
If any of them gets faulty, an effective charge will not be produced.
This will end up affecting the combustion in the combustion chamber.
As a result of this, the outboard motor will not be able to start.
But when the faulty stator or ignition coil is replaced with a good one, then the outboard motor wil start flawlessly.
2) Outboard Motor Vibrating When Accelerating
At some point you may face an issue in which your outboard motor is vibrating when accelerating.
This is always very unpleasant.
It slows down the journey and also creates a discomfort as a result of the vibrations.
a) Bad Spark Plug
For the outboard motor to function, power has to be produced to turn the propeller.
This power production originates from the engine.
This is made possible by components like the spark plug.
If the spark plug is bad, then there will be no power production from that cylinder.
This will lead to less and unbalanced power production and will cause vibrations when the outboard motor is in use.
b) Bad Fuel
The quality of fuel used in an outboard motor plays a vital role in the functionality of the outboard motor.
If a good fuel is used, then the outboard motor will perform flawlessly.
But if a bad quality of fuel is used, then the performance of the outboard motor will suffer.
This is because when a bad fuel like the one that contains water is used, the combustion will be poor in the combustion chamber.
This will affect the power that is produced too and causes vibrations.
c) Loose Outboard Positioning
When an outboard motor is in use, there is always an up and down motion in the combustion chamber.
This causes some vibrations.
But this is rarely noticed if the outboard motor is properly mounted.
If the outboard motor is not properly mounted, the vibrations will be well felt by people in the boat.
3) Mercury 40 Hp Overheating
Another problem with mercury four stroke 40 hp is overheating.
This is the excessive rise in temperature than what the engine is made to function with.
This is always a serious problem and can lead to the damage of some parts.
At worse cases, it can lead to the total destruction of the outboard motor.
a) Faulty Cooling System
As the outboard motor functions, there will be power generated from the engine.
This is due to combustion in the combustion chamber.
Due to this, heat is being generated.
To avoid damage of any of the mercury 40 hp parts, a cooling syatem helps to reduce the temperature.
But when the cooling system like the impeller is bad, then there will be an overheating in the outboard motor.
a) Fix Faulty Cooling System
When you discover that you are facing an overheating problem, you have to troubleshoot.
This will help you find the faulty part.
It could be that the hose that transports the cold water is clogged or that the impeller is faulty.
When you discover the faulty part, you have to make sure that you replace it with a good one.
This will help solve the overheating problem.
4) Carbon Build Up
When there is combustion in the combustion chamber, there are always bye products.
One of such is carbon and some toxic gases.
These are released out of the outboard motor from the exhaust pipe.
But the thing is that they are not usually 100% removed.
Some will still be left over.
As the outboard motor continues in use, this carbon build up gets worse and can impart on the functionality of the outboard motor negatively.
a) Lack Of Proper Maintenance
During the maintenance of an outboard motor, one of the things that is done is the removal of built up carbon.
This will help the outboard motor to function well.
But when an outboard motor is used for an extensive period of time without proper maintenance, then this carbon increases.
This leads to an excessive carbon build up in the outboard motor which will affect the performance of the outboard motor.
a) Perform Timely Maintenance
When you discover that there is a carbon build up in your outboard motor, you have to contact a technician for a maintenance servicing.
This will help remove the excess carbon from the outboard motor.
5) Engine Shutting Down On High Acceleration
Another mercury 4 stroke 40 hp problem that occurs is shutting down of outboard motor when accelerating.
This is usually dangerous and can leave the passengers in the boat stranded if not fixed.
a) Bad Cylinder
When it comes to the mercury 4 stroke 40 hp, it is built to perform well.
But as time goes on, some of the components in the outboard motor will loose efficiency.
This can occur in the cylinder of the outboard motor.
When this occurs, then the cylinder will lose compression.
Due to this, there will be issues in the performance of the outboard motor.
This will show up in situations like the outboard motor shutting down when accelerating.
b) Bad Spark Plug
Spark plugs are very important in the functionality of an outboard motor.
For power to be produced from the combustion chamber, the spark plug helps deliver electric charges for combustion.
But when the spark plug is bad, then there will be an incomplete or no combustion.
This will affect the power generated from the outboard motor.
It is felt more when you try to accelerate.
At such point, the outboard motor will just shut down as it cannot generate the power needed.
c) Bad Fuel
Using a bad fuel in your outboard motor will affect how it performs.
If you use a bad fuel, then the combustion in the combustion chamber will not be effective.
This will lead to power generation problems when using the outboard motor.
a) Use Good Spark Plugs
If you want to have a flawless performance from your outboard motor, you have to make sure that you use a good spark plug.
This will help the outboard motor to generate the needed power and avoid shutting down when accelerating.
b) Use a Good Fuel
As much as you can, always stay away from the use of bad quality fuel in your outboard motor.
A bad fuel reduces the efficiency of your outboard motor.
A bad fuel will also reduce the lifespan of your outboard motor too.
To avoid this and cases like the outboard motor shutting down when accelerating, you have to always use a good fuel.
6) Propeller Problems
The propeller is a very vital component of an outboard motor.
It is what makes the outboard motor to move a boat.
But as you continue making use of your outboard motor, one of the parts that will loose efficiency is the propeller.
This is one of the mercury 4 stroke 40 hp problems that you will encounter.
a) Use In Shallow Water
The propeller is the lowest part of an outboard motor.
This makes it the part that suffers a great damage when an outboard motor is used in a bad water.
This can be a water body that is too shallow or filled with rocks.
In such a scenario, the propeller will easily make contact with the bottom of the water or hit the rocks.
This is always very bad and will end up damaging the propeller of the outboard motor.
b) Poor Storage
After using your outboard motor, you have to make sure that you store it.
The way you store it plays a vital role in the longevity of your outboard motor.
If properly stored, your outboard motor will last long.
But if you do not store it well, then your outboard motor parts like the propeller will be easily damaged.
a) Avoid Extremely Shallow Water
When using your mercury 40 hp outboard motor, you have to make sure that you avoid extremely shallow waters.
Driving on extremely shallow waters will end up destroying the propeller easily.
To avoid this, you have to make sure that you stay away from shallow waters when using your outboard motor.
b) Store Outboard Motor Well
It is a necessity to make sure that you store your outboard motor after use.
But in doing so, you have to make sure that you do it the right way.
This will help save your outboard motor parts like the propeller from damage.
7) Mercury 40 Hp Propeller Pushing Out Too Much Water
As your outboard motor functions, the propeller will be in a circular motion.
This will help provide the force needed to push the boat in the forward or backward direction.
As the propeller rotates, it will displace some amount of water above the water surface.
But when the amount of water displaced above the water surface is too much, you have to check the height of the outboard motor.
Excessive displacement of water by the propeller is a sign that the outboard motor is not well mounted.
a) Outboard Motor Is Mounted Too High
When you discover that your propeller is pushing too much water above the water surface, it is due to the outboard motor being mounted too high.
This causes the propeller to push out too much water as it rotates.
a) Mount Outboard Motor Properly
When you discover that your outboard motor is mounted too high, you have to make an adjustment.
This is done by making the outboard motor to go further below.
To get this height right, you have to make sure that you check for heights recommended by the outboard manufacturer.
This will help your propeller to move the boat well instead of displacing excess water above the water surface.
8) Mercury 4 Stroke 40 HP Problem Of High Fuel Consumption
You should not expect a 40 hp outboard motor to consume fuel like a 1 hp outboard motor.
But that does not mean that a 40 HP mercury outboard motor has to consume 10 gallons of fuel per minuite.
When this occurs, it is purely a high fuel consumption.
As your mercury 40 hp outboard motor ages, this is one of the problems you may encounter.
a) Outboard Age
As your outboard ages, it will not perform as it used to perform when it was new.
One of the ways this will show up is in the fuel consumption.
When an outboard gets older, it will consume fuel a bit higher than it used to consume.
b) Oil Issue
The oil in the outboard motor performs a very vital role in the functionality of the outboard motor.
It helps in the lubrication process.
It also helps in the control of temperature too.
But to achieve this, you have to use a good oil.
Without that, you are going to have issues.
This will show up in a higher fuel consumption when you do not change the oil on time or if you use a bad one.
c) Lack Of Maintenance
Timely maintenance helps in keeping your outboard motor in a good working condition.
This involves tasks like changing the oil and other tasks.
But if you delay the maintenance period, you will run into some issues that will affect the performance of your outboard motor.
This includes issues like a higher fuel consumption.
a) Use a Good Oil
When you change the oil in your mercury 40 hp outboard motor, you have to make sure that you use a good oil.
This will help improve the performance of your outboard motor.
With a good oil in your outboard motor, you will experience a good mileage when you use your outboard motor.
b) Perform Timely Maintenance
If you want your outboard motor to run flawlessly, you have to make sure that you perform maintenance on time.
This includes task like changing the oil in the outboard motor.
With this, your outboard motor will be able to perform well.
You will also experience a better mileage when you perform maintenance on your outboard motor on time.
This is one of the best ways to reduce mercury 4 stroke 40 HP problems.