Common Mercury 50 HP 4-Stroke Problems [with fixes]

Mercury 50 HP 4-stroke is incredibly powerful, efficient, and easy to use, making it an excellent choice for experienced boaters and first-time buyers. It is capable of reaching speeds of up to 30 to 35 mph. Another quite impressive thing about the Mercury 50 HP 4-stroke outboard is its fuel efficiency. Thanks to its 4-stroke engine, this outboard can run for up to 1 hour on a single gas tank. 

But there can also be a few issues with a Mercury 50 HP 4-stroke outboard engine, such as the fuel system, spark plugs, oil, and more. In this guide, we will go over some potential problems that could occur with a Mercury 50 HP 4-stroke outboard engine and ways to fix them. 

#1 Misfire

If you have a 50 mercury 50 hp four stroke that is misfiring, there are several potential causes. Let’s look at some of the most common causes of engine misfires and how to fix them.

Carbot deposit

Several things can cause engine misfires, but most often, it is due to a build-up of carbon deposits on the spark plugs or in the combustion chamber. This can be remedied by regularly cleaning the spark plugs and combustion chamber.

Bad spark plug

If a spark plug is fouled or damaged, it can cause the engine to misfire. Replacing the spark plug is often needed to fix the problem.

Clogged air filter

A dirty or clogged air filter can restrict airflow to the engine, causing it to run lean and misfire. Cleaning or replacing the air filter is usually all needed to fix the problem.

Running Lean

If the engine is running too rich, this can also cause misfires. Many things, including a leaking fuel injector, a dirty air filter, or a defective oxygen sensor, can cause a rich mixture. Replacing the leaking fuel injector or cleaning the air filter is often all needed to fix the problem. If the oxygen sensor is defective, it will need to be replaced.

#2 Overheating 

If your Mercury 50-hp four-stroke engine is overheating, there are a few things you can do to fix the problem. But the first thing you need to do is check the oil level and add oil if necessary once the engine has cooled down. Restart the engine and run at a lower speed until it reaches the average operating temperature.

The reason

Overheating in a marine engine happens most often due to a build-up of debris in the cooling system. But it can also be caused by a faulty thermostat, a restricted cooling system, or a defective water pump. 

How to fix It

Check the thermostat. 

A stuck can cause the engine to mercury 50 hp  overheat. You can replace the thermostat yourself or take the engine to a Mercury dealer or qualified mechanic to have it done. 

Clean the cooling system. 

You should also Check for a leaking cooling system, as it can cause the engine to overheat. Because often a build-up of dirt and debris in the cooling system can cause the engine to overheat. So if you can, then clean the system yourself, or take the engine to a Mercury dealer or qualified mechanic to have it done.

Replace the engine oil. 

If the engine oil is dirty or low, it can cause the engine to overheat. You can check the oil level and quality yourself or take the engine to a Mercury dealer or qualified mechanic to have it done.

#3 Noise 

Another common issue is that the engine can develop a knocking noise. This is usually caused by loose parts such as piston rings, worn valve seals, loose mufflers, etc. If you have a mercury 50 hp four-stroke engine, common causes of engine noise include the following:

Loose Parts: 

Over time, certain bolts and nuts holding your engine together can work themselves loose. This can cause rattling and other noise. Check all engine bolts and nuts periodically and retighten them as needed.

Worn Engine Mounts: 

The rubber mounts isolating your engine from your boat can degrade over time. This can allow more engine vibration to be transferred to the hull, resulting in more noise. Inspect your engine mounts periodically, and replace them if they show signs of wear.

Worn Out Pulleys: 

The pulleys in your engine’s cooling system can wear out over time, resulting in increased noise. Inspect your pulleys periodically, and replace them if they show signs of wear.

Worn Out Bearings: 

The bearings in your engine can wear out over time, resulting in increased noise. Inspect your bearings periodically, and replace them if they show signs of wear.

Incorrectly Installed Exhaust System: 

If your engine’s exhaust system is not installed correctly, it can also cause increased noise. Be sure to have a qualified technician inspect and, if necessary, correct your exhaust system.

# Oil Leak

You might not know it, but that tiny oil leak in your Mercury 50-hp 4-stroke engine could be doing some serious damage. Oil is essential for lubricating your engine and keeping it running smoothly. But when oil leaks, it can cause all sorts of problems. Not only will it make your engine run less efficiently, but it can also lead to costly repairs down the road.

One of the most dangerous things about oil leaks is that they can easily go undetected. If your engine is leaking oil, likely, you’ll only notice it when it’s too late. Oil leaks can often cause your engine to overheat, leading to engine failure.

The reason

There are many possible causes for an oil leak in your Mercury 50 HP 4-stroke engine, but the most common cause is a faulty oil seal.

How to Fix it

The very first thing you should do is check the oil level in the engine and whether the oil level is low or high. If the oil level is low, you will need to add oil to the engine. But you will need to drain the excess oil from the engine if the oil level is high.

As you have checked the oil level, you will need to identify the source of the leak. The most likely source of the leak is the oil seal. The oil seal is located between the engine and the oil pan. It is responsible for sealing the oil in the engine and preventing it from leaking.

Once you have replaced the oil seal, you will need to check the oil level in the engine again. If the oil level is still low, you may need to add oil to the engine.

If the oil leak is still present even after replacing the oil seal, you may need to check other potential sources of the leak. These include the oil filter, the oil pan gasket, and the engine oil.

#Coolant Leak 

The reason

Among all the things that can cause a coolant leak in your Mercury 50-hp 4-stroke engine, the most common reason is a faulty gasket or O-ring. These can eventually wear out and leak, especially if not properly maintained. Another possibility is a crack in the engine block or cylinder head. These cracks can be caused by various things, including overheating, physical damage, or even age

.

How to Fix it

If you suspect that you have a coolant leak, the first thing you should do is check the engine oil. If the oil looks milky or has a reddish tint, that’s a good indication that coolant is leaking into the oil. Once you’ve confirmed a leak, you’ll need to figure out where it’s coming from.

If the leak is small, you can fix it with a sealant. Many sealants on the market are specifically designed for repairing coolant leaks. Just follow the instructions carefully and only use the sealant on clean, dry surfaces.

For larger leaks, you’ll likely need to take your engine to a mechanic or for repairs. The mechanic may be able to repair the leak by welding or using a special sealant.

#Faulty ignition system

Mercury 50 hp 4 stroke engines are known for their faulty ignition systems. The Ignition system is responsible for providing the spark that ignites the air/fuel mixture in the engine’s cylinders. A faulty ignition system can cause the engine to misfire, run roughly, or stall. Many different things can cause the ignition system of your mercury 50 hp 4 stroke to fail, such as:

The reasons and How to Fix Them

Faulty Spark Plugs

The spark plugs are responsible for creating the spark that ignites the fuel in the cylinders. But spark plugs will eventually become damaged and fail, causing a faulty ignition system in your mercury 50 hp 4 stroke engine.

Dirty Or Faulty Ignition Coils

The ignition coils provide the high voltage needed to fire the spark plugs. Over time, the coils can become dirty or damaged, causing them to fail.

Worn Out Distributor Cap And Rotor

The distributor cap and rotor distribute the high voltage from the ignition coils to the spark plugs. But once these distributor caps and rotor can are worn out, it can lead to a faulty ignition. system. 

Mercury 50 Hp 4 Stroke Maintenance Checklist 

Parts Needs to Be changedWhen To Change
Oil and oil filter50 hours of use 
Spark plugs and air filter100 hours 
Lower unit gear lubeOnce a year

Final Words

Please remember that this is not an exhaustive list but rather a snapshot of some of the more frequently seen problems in a mercury 50 hp four stroke or most marine engines. But one simple way to avoid most of these problems is to maintain your Mercury 50 HP 4-stroke outboard motor properly. 

One of the  important maintenance tasks to keep up with is keeping the engine clean. This means regularly washing the mercury 50 hp 4 stroke using fresh water and also flushing it with specifically designed saltwater gear. Mercury recommends that you wash and flush your engine every 20 hours of use or once a month, whichever comes first.

Share

Leave a Reply