Mercury 115 Four Stroke Motor Problems – 6 Common Issues And Solutions

mercury 115 four stroke problems
mercury 115 four stroke problems

From acceleration to efficiency, you need to look at multiple features while trying to pick the perfect motor for your boat. There are many great brands like Minn Kota that you can use on a daily basis.

If you’re a beginner and don’t know much about boat motors, it is best to rely on expert opinion and try the motors yourself. That way, you will get many options for your boat that will provide optimal per menace according to the water conditions.

With that said, many people rely on Mercury motors as the primary option for their boats. It is true that these motors provide top performance, but there are some minor issues that you can expect in the long run.

So, let’s cover a few common problems of Mercury 115 Four Stroke motors to help you make a better decision.

Common Mercury 115 Four Stroke Motor Problems

  1. Unit Not Holding Charge

Issues with the system not holding charge are quite common with the mercury 115 Four stroke motor. Luckily, most of the time, this issue is related to problems with the connection points as well as the wiring.

So, if your unit is not holding a charge properly, it is best to start with the inspection of connection points and the wiring cluster in your unit.

charge battery

Cleaning the connection points should be enough to help you get around this issue. Make sure that every bit of dirt or corrosion is removed from the connection points.

You can rely on the use of a brush with a little bit of vinegar for this task. There are also many cleaning products in the market that will help you keep the connection points in perfect condition.

Similarly, if there is nothing wrong with the connection points, then it might be a good time to inspect the wiring cluster.

You have to check for any possible physical damages and ensure that the wires are in perfect shape. You can also use a multimeter to find the faulty wires in the system if the issue is not fixed at this point.

  1. Engine Losing Power

One of the most annoying things that you have to deal with is the engine losing power. You are not able to maintain high speed with the motor, and whenever there is excessive load on the system, it shuts down.

If you’re in a similar situation, then there is a good chance this issue was caused by overheating problems or clogging in the water separator.

power button

It can be somewhat complicated for beginners to fix this problem, so rely on professional help if you’re inexperienced.

If the issue is related to the unit overheating, then you should start with the inspection of the water pump. If there are any visible damages to the pump, try to get a replacement for the unit.

Otherwise, you might end up causing permanent damage to the pump if you don’t take care of the overheating issue in time. Make sure to take a look at the cooling section to see if any valve broke or not.

Aside from this, a clogged water separator can also create issues with a loss of power. If that is the case with your unit, contact your dealer or take the motor to an expert. He will take care of the water separator issue in no time.

  1. Fuel Pump Issues

There are many reasons that can lead to issues with the fuel pump in your Mercury 115 Four Stroke motor. The majority of the time, these issues are related to users using bad-quality fuel in their units.

Other than that, avoiding the use of a fuel stabilizer also leads to similar issues with the fuel pump. So, if you’re struggling to manage the fuel system of your unit, try managing the fuel supply properly.

 fuel tank

The first thing you should do is dump out the old fuel and then add premium-grade fuel to the unit. Along with that, you need to use a recommended proportion of fuel stabilizers in the unit to keep everything working.

Following this method will not only fix the pump issue, but you will also be able to achieve better performance with the system.

You should also look at changing the fuel filter in your unit. It is an inexpensive fix and will help you get around performance-related issues. Hopefully, this information helps you make a better purchase decision about the boat motor.

  1. Timing Belt Issues

Next, you need to check the condition of the timing belt to isolate errors with the system. If you’re not getting any response from the unit and purchased it from the second-hand market, then check the condition of the timing belt.

If you do find it in rough condition or swollen by oil, it might be time to get a replacement. You can find a compatible replacement at any authorized dealer, and the installation is not that hard.

It all comes down to keeping the hardware in good shape, and ignored maintenance will wear out this belt sooner.

While a bit of rough patch on the belt or a small spot won’t do you any hard, keeping a damaged belt for an extended period will create more issues down the road.

So, if you’re trying to avoid these issues, be sure to be proactive, and address this situation.


The upside here is that the replacement should come pretty cheap, and the belt can be installed with minimal effort. So, even if you don’t know much about this machine, going through the manual instructions won’t be that hard.

From there, you can recheck the performance of the Mercury system, and it will respond accordingly. Hopefully, you won’t have to deal with more errors, and this unit will keep working.

  1. Lubrication Problems

Issues with the motor can also stem from ignored lubrication requirements. If you don’t know how to lubricate the required sections or can’t really find the fitting for the support lever, try reading the manual one more time.

You can also seek help from an expert, and using decent lubrication on the fittings, shafts, and tilt tube will help you keep the unit in perfect shape.

Otherwise, you will notice a delayed response or excessive wear on the joints maintained by this machine. So, be sure to lubricate your unit monthly.


Keeping track of the lubrication requirements is not that hard, and you have to apply a little bit every week for optimal performance.

This won’t only keep the unit in good shape, but you will also notice a smoother response from the machine. So, be sure to spare some time each week for this process.

  1. Fuse Problems

Wiring and the fuses have always been an issue for this model. This problem is usually not that serious, and a quick clean-up of the connectors and the replacement of the fuse will help you get through the error.

All you have to do is to narrow down the issue with the fuse by using a voltmeter.

From there, you can adjust and then recheck the response from the unit one more time. Hopefully, maintaining the connectors and changing the fuses will help you get through the power issues.

If you’re unable to fix this issue yourself, then hiring an expert is a good idea. He will help you get through the error in no time. So, spare a few bucks and hire an expert to help with the situation.

Wrapping Up

Almost all of these errors are easy to avoid when you’re aware of the basic maintenance requirements. The unit won’t be able to respond to any input when the device is in poor shape.


So, it might not be a genuine situation with the unit, and you need to keep track of the maintenance.

A bit of maintenance will go a long way when it comes to securing consistent performance. It might be a bit of a hassle at first, but you won’t have to spend more than a few minutes each week once you’re experienced.

So, be sure to ask for pointers if you’re not sure about how to manage the system.

With that said, the fixes mentioned here are not that hard to fix. You will just need a basic knowledge of engines, and replacing filters as well as connectors will do the job. Just be patient and thoroughly inspect the system before making any rash decision.

Hopefully, you won’t have to bother with a replacement, and the Mercury unit will start working after you get through the fixes mentioned above. 

1 thought on “Mercury 115 Four Stroke Motor Problems – 6 Common Issues And Solutions”

  1. Mercury 115 motor…..About a year ago, I had problem with loss of power and then complete shutdown. Fuel pressure regulator problem which they think burned out the fuel pump. Motor ran fine after that but it felt like it didn’t have the same power as before. 3rd Mercury motor and it will be the last!


Leave a Comment