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Yamaha 115 4 Stroke Problems & Solutions – Easy Fix

Yamaha 115 4

It’s super annoying when the motor stops working all of a sudden. We totally understand that. But sitting around and getting mad isn’t going to solve the situation. So, when an issue occurs, you ought to fix it right away.

So, what are these Yamaha 115 4 stroke problems?

Among many Yamaha motor problems, the engine not starting up is the most common. One of the key reasons behind that is a dead battery. Also, faulty spark plugs will interrupt the ignition. Other than that, it could be a clogged fuel line jamming the fuel supply. Lastly, you may have to clean and adjust the carburetor.

Anyways, that was nothing but a short preview. Stay with us if you wish to know more about Yamaha 4 stroke problems.

So, let’s not beat the bush around and head right in-

Yamaha 115 4 Stroke Troubleshooting: 4 Problems & Fixes

Yamaha has been making top-of-the-line motors for decades. Even though Yamaha motors are one of the best, they aren’t perfect. Similarly, the Mercury 115 Pro xs has its share of problems too.

So, to help you out, we’ve listed all sorts of problems and their solutions.

Problem 1: Dead Batteries Can’t Start Up an Engine

Whenever a problem occurs, some completely forget to check on their boat batteries. Although it may not happen in your case, you can’t overlook it at all.

There are two batteries in a boat. They are called the starting battery and deep cycle battery. These batteries have two different tasks.

The starting battery starts up the engine. On the other hand, the deep cycle battery powers up the electrical system.

batteries in a boat

Solution: Check and Replace the Battery

Checking a battery is super easy. You’re only going to need a multimeter for this one.

Start with locating the battery on your boat. Usually, it’s on the backside of the boat. Also, you can use the boat manual to easily find the battery.

Now, get the multimeter and place the black node on the negative. After that, put the red one on the positive and see the reading.

A healthy 12V battery will have a 12.6-volt reading. If you’re seeing less than 12.6, the battery might be faulty. Also, if it’s around 10.5 volts, the battery must be replaced.

So, if you’re getting a bad reading, you’ve to replace the battery. Luckily, this is a really easy task.

First, take the battery cap off the box if there are any. Then detach the negative and positive cables from the battery. Make sure both cables aren’t touching any metals or each other.

When that’s done, take out the battery and put in a new one. Then place the positive and negative cables correctly. Lastly, put the lid back on and try starting the engine!

Also, boats tend to stay inactive for a long time. In that case, you can have a battery retainer connected. It’ll keep your battery alive during inactivity.

Problem 2: Faulty Spark Plugs Halts the Ignition

For the best performance, a good marine spark plug is always required. But if they are dirty or faulty, they can’t execute the ignition. As a result, the engine doesn’t boot up.

Solution: Check & Replace the Spark Plugs

Like before, we’ve to check on the spark plugs first before replacing them. It only takes 1-2 minutes. The spark plugs may show different symptoms and they have different meanings.

Yamaha 115 4 Faulty Spark Plugs Halts

To save you some time and effort, we’ve made a small table for you-

Spark Plug Symptom Probable Cause What To Do
Wet Spark Plugs Water mixed with fuel Must be replaced
Dry Spark Plugs None Spark plugs are fine
White Residue on Spark Plugs Overheating Must be replaced
Black Sooted Spark Plugs Too much Oil Should be cleaned or replaced
Eroded Spark Plugs Overheating Must be replaced

So, you’ve to change the spark plugs if it’s showing one of these symptoms. Don’t worry too much though.

Installing the spark plug is easy. Plus there are similarities between Yamaha and Mercury spark plugs wires installation. So, it’s kind of the same for every boat.

Furthermore, it only takes a while to do it. The plugs are easily affordable too.

Now, you can grab whichever you like the most and get started instantly!

Problem 3: Clogged Fuel Line Doesn’t Let Fuel Through

Another common issue that even professionals tend to forget is the clogged fuel lines. Also, if you use Ethanol as fuel, it’ll degrade the fuel line.

As a result, fuel line particles will mix with oil and clog the line.

Solution: Use Regular Gas Instead of Ethanol

If you’re using fuel that contains ethanol, get rid of them as soon as you can. After that, you’ve to buy some regular gas instead.

Because while ethanol may be cheaper, it’s not necessarily good for your fuel hose. Especially when an engine stays idle.

Nevertheless, regular gas might be a little too pricey. But unfortunately, there are no alternatives for this. So, for the betterment, you’ve to sacrifice a little bit.

Another method is to get good marine fuel lines. They last longer than normal ones and maybe just what you need.

Problem 4: Dirty Carburetor Interrupts the Oil Flow

Yamaha 115 4 oil

The carburetor may be quite small but it plays an important role. Without a healthy carburetor, the engine will never operate at its maximum efficiency.

Solution: Clean the Carburetor

Due to being small, the carburetor can easily get clogged by dirt or gunk. So, you’ve to be precise while cleaning it.

First, remove the carburetor from the engine. To do that, detach the linkage on both sides. After that, undo the top 4 screws and take the cap off. You can use a soft cloth or any picks to get the dirt out of there.

While doing this process, you can take pictures of the screw’s positions. In this way, you won’t mess up the adjustment.

When the top is done, unscrew the bottom screw and uncap the bottom lid. The fuel will start pouring but that’s fine. Clean the carburetor and make sure it’s getting crystal clean.

Now, put the parts back together and you’re done. Try starting the engine. For most people, this should solve the problem.

Also, sometimes, bad adjustments of a carburetor can interrupt oil flow. That’s why you’ve to make sure the carburetors are adjusted properly.

Finally, if all these seem too much of a hassle to you, just hire the professionals. They will easily find your problem and solve it.

Problem 5: Bad Fuel Pump

When your Yamaha boat engine is not supplying the correct fuel to the cylinders, it can cause a number of problems. These can include decreased performance, poor running conditions, and even catastrophic failure.

The most common issue with fuel pumps is that they can become clogged or worn out over time. This can cause them to stop working altogether, which will lead to decreased performance and possible engine failure.

Solution: Check for leaks and codes

A leaking fuel pump can cause serious damage over time and could even lead to a fire. Inspect all hoses and connections for signs of leakage.

Also, if your pump isn’t working but you’re still having issues with your engine, check for codes related to fuel injection systems in your dashboard computer. These codes may give you some indication of what’s wrong with your pump.

Yamaha 115 4 leaking fuel pump


Question: How many hours can a Yamaha 4 stroke last?

Answer: Yamaha motors are one of the most long-lasting motors ever made. They usually last around 5500 hours to 7000 hours.

Question: How fast does a Yamaha 115 go?

Answer: Among many Yamaha motors, the 115 is praised a lot. One such reason behind that is its top speed. A normal Yamaha 115 4 stroke can reach up to 51 mph or 82.07 kph. It’s one of the fastest Yamaha motors without a doubt.

Question: Is a 4 stroke more powerful than a 2-stroke?

Answer:  In simple words, the 2-stroke is more powerful. A 4-stroke engine has a lower RPM but it can still produce high torque. On the other hand, a 2-stroke has a higher RPM to reach a high torque. But a higher RPM will kill the engine faster.

Final Words

That was all we could gather on Yamaha 115 4 stroke problems. Hopefully, your confusion has been cleared and now you know what to do.

Finally, last but not least, good luck with your motor!

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