Like all other engines, with a Mercury 115 2-stroke outboard, you will face some common issues. as a user myself, I often face problems with the engine from time to time. Recently I have encountered some new problems, so here I am, updating the article again.
so, what are the common Mercury 115 2 Stroke problems?
the common problems with Mercury 115 2 Stroke include,
- Not Running on 4 Cylinder
- Intermittent Beeping
- 2+2 Carburetor problems
- Outboard Won’t Throttle
- Stroke Not Peeing
- Misfire Problem
- motor won’t get past 3000 RPM
In this article, I’ve explained all these Mercury 115 2 stroke Problems with proper solutions. So, keep reading
Mercury 115 2 Stroke Not Running on 4 Cylinder
If a Mercury 115 2-stroke outboard engine is not running on #4 cylinder, this can indicate several potential issues. Below are some of the possible reasons and solutions for this 115 hp mercury outboard 2 stroke problem:
| Reason | Solution |
| Issue with the spark plug | Install the spark plug tightly and gap correctly |
| Issue with the fuel delivery | Make sure that the fuel line is clear |
| Problematic compression | Contact the mechanic |
| Electrical issue | Replace the faulty component |
Reason 1: Spark plug issue
A faulty or fouled spark plug can cause cylinder #4 to stop firing. To resolve this issue, remove and inspect the spark plug, replacing it if necessary. Ensure that the spark plug is gapped correctly and installed tightly.
Reason 2: Fuel delivery issue
If the fuel injector for cylinder #4 is clogged or not delivering fuel, the cylinder will not fire. To address this issue, check the fuel injector and fuel line for any blockages or damage. Clean or replace the fuel injector as needed, and make sure that the fuel line is clear.
If you are looking for cleaning instructions for a fuel injector, check out the video –How To Clean Your Outboard Fuel Injectors At Home (Easy Way)
Reason 3: Compression problem
If there is low compression in cylinder #4, it may not fire properly. Check the compression in all cylinders using a compression gauge, and compare the readings to the manufacturer’s specifications.
If cylinder #4 has low compression, it may be due to worn or damaged piston rings, a damaged cylinder wall, or a damaged head gasket. These issues require more extensive repairs, and it may be necessary to seek the assistance of a qualified mechanic.
Reason 4: Electrical issue
If there is a problem with the electrical system, such as a faulty coil or CDI module, cylinder #4 may not receive the proper spark to ignite the fuel. Check the ignition system and wiring for any damage, and test the coil and CDI module. Replace any faulty components as needed.
An electrical system malfunction is also very common among the blue wave boat. A few days ago I posted another article about the issues of blue wave boats. If you want you can give it a check.
Mercury 115 2 Stroke Intermittent Beeping
When a Mercury 115 2-stroke outboard engine emits an intermittent beeping sound, it can be an indicator of a problem. This beeping can be caused by several potential issues, such as low oil level, overheating, low battery voltage, faulty sensors, or wiring issues.
| Reason | Solution |
| Low oil level | Fill the tank with oil |
| Overheating | Remove blockage from the cooling system |
| Low Battery Voltage | Recharge or replace the battery |
| Faulty Temp or Oil Sensor | Replace the sensors |
| Wrong Wiring | Replace the corroded and damaged wires |
Reason 1: Low Oil Level
Low oil level can cause the engine to beep intermittently. If the oil level in the oil tank is low, the engine may beep to alert the operator to the issue. A low oil level can lead to engine damage and eventual failure. To resolve this issue, check the oil level in the oil tank and add oil as needed. It’s also a good idea to check the oil lines and fittings for any damage or leaks that could lead to a loss of oil.
Reason 2: Overheating
Overheating is another potential cause of intermittent beeping in a Mercury 115 2-stroke outboard engine. An overheating engine can be caused by a variety of issues such as a clogged water intake, a damaged water pump impeller, or a failing thermostat.
Overheating can lead to engine damage, so it’s important to address this issue as soon as possible. To address this issue, check the engine’s cooling system for any blockages or damage. Replace any faulty components and ensure that the engine is receiving adequate cooling.
Reason 3: Low Battery Voltage
Low battery voltage is another potential cause of intermittent beeping of the mercury 115 outboard 2 stroke. Low voltage can also cause other electrical issues with the engine, such as difficulty starting or running. To address this issue, check the battery voltage using a multimeter, and recharge or replace the battery as needed.
Reason 4: Faulty Temp or Oil Sensor
Another potential cause of a Mercury 115 2-stroke outboard engine emitting an intermittent beeping sound is an issue with the temperature sensor or oil level sensor. If the temperature sensor is malfunctioning, it may send false signals to the engine’s computer, causing it to beep intermittently. This can occur if the engine is overheating or if the sensor itself is faulty.
Similarly, if the oil level sensor is acting up, it may also send false signals to the engine’s computer, causing the engine to beep intermittently. This can occur if the oil level is low or if the sensor itself is faulty.
To solve the issue, test the sensors and replace any faulty sensors as needed.
Reason 5: Wrong Wiring
Wiring issues, such as a damaged or corroded wire, can also cause the engine to beep intermittently. Inspect the wiring harness and repair or replace any damaged or corroded wires.
1991 115 Mercury 2+2 Carburetor problems
The 1991 115 Mercury 2+2 outboard engine can experience carburetor problems that affect the performance of cylinders 3 and 4. Symptoms of this problem may include rough idling, difficulty starting, and reduced power at low RPMs. In some cases, cylinders 3 and 4 may be inoperative until 2000 RPMs, at which point they come online, but the transition is very rough and sounds like the cylinders are misfiring.
| Reason | Solution |
| Clogged or dirty carburetor | Clean the carburetor properly |
| Faulty carburetor or fuel pump | Repair for minor issues or replace it |
| Faulty ignition system | Replace the spark plug wires or the spark plug |
Reason 1: Clogged or dirty carburetor
One potential cause of this issue is a clogged or dirty carburetor. Over time, dirt, debris, and varnish can accumulate in the carburetor and block the fuel passages, leading to reduced fuel flow and poor performance. To resolve this issue, the carburetor will need to be removed and cleaned thoroughly.
Reason 2: Faulty carburetor or fuel pump
Another potential cause of this issue is a malfunctioning carburetor or fuel pump. If the carburetor or fuel pump is not functioning properly, it may not be delivering enough fuel to cylinders 3 and 4, leading to reduced performance. The carburetor and fuel pump will need to be inspected and replaced if necessary.
Reason 3: Faulty ignition system
Additionally, a faulty ignition system can also cause misfiring in cylinders 3 and 4. The spark plugs, spark plug wires, and ignition coils should be inspected and replaced as needed.
Mercury 115 2 Stroke Outboard Won’t Throttle
There could be several reasons why a Mercury 115 outboard motor won’t throttle and stall when given gas. Here are some possible causes and solutions:
| Reason | Solution |
| Fuel System Issues | Clean the fuel filers or replace |
| Carburetor Problems | Clean the carburetor or replace |
| Throttle Cable Problems | Replace the damaged throttle cable |
| Lower Unit Issues | Rebuild or replace it |
| Ignition System Issues | Check and replace the ignition coils and spark plug |
Reason 1: Fuel System Issues
Check if the fuel tank has enough fuel and the fuel line is not clogged or damaged. Also, inspect the fuel filters and replace them if they are dirty or clogged. If these components are found to be in good condition, then the fuel pump may be faulty and needs to be replaced.
Reason 2: Carburetor Problems
If the carburetor is not functioning correctly, the motor may not be getting enough fuel. Inspect the carburetor for any signs of clogging, dirt, or corrosion. Try cleaning it with a carburetor cleaner, or if the damage is severe, replace the carburetor.
Reason 3: Throttle Cable Problems
Check the throttle cable and make sure it’s not loose, stretched, or broken. If it’s damaged, replace it.
Reason 4: Lower Unit Issues
Check if the lower unit is damaged or corroded, which can cause poor performance and throttle issues. If it’s damaged, it may need to be rebuilt or replaced.
Reason 5: Ignition System Issues
If the spark plugs are fouled, damaged, or worn out, it can cause poor combustion, resulting in the engine stalling when given gas. Check the spark plugs and replace them if necessary. Also, inspect the ignition coils and wires for damage, and replace them if needed.
Mercury 115 2 Stroke Not Peeing
This is a common 1998 and 2004 Mercury 115 2 stroke problem. If your Mercury 115 2-stroke outboard engine is not “peeing,” which refers to the water stream that should come out of the tell-tale hole, there could be several reasons why this is happening. Here are some common causes and potential solutions:
| Reason | Solution |
| Blockage in water intake | Check and remove any debris or blockages in the water intake |
| Water pump failure | Replace the water pump and inspect the impeller for damage or wear |
| Clogged tell-tale hole | Check and clear any debris in the tell-tale hole |
| Faulty thermostat | Replace the thermostat and check if the water flow has been restored |
| Cooling system leak | Check for and repair any leaks in the cooling system, then refill with the appropriate coolant |
Reason 1: Blockage in the water intake
This is the most common cause of no water flow. Check the intake for any debris or blockages that may be preventing water from entering the engine. Remove any obstructions and clean the intake.
Reason 2: Water pump failure
The water pump may have failed, which can be caused by wear and tear, lack of use, or debris getting caught in the impeller. Replace the water pump and inspect the impeller for any damage or signs of wear.
Reason 3: Clogged tell-tale hole
Check the tell-tale hole for any debris that may be blocking the water flow. Use a small piece of wire or a toothpick to clear the hole.
Reason 4: Faulty thermostat
The thermostat may be stuck in the closed position, preventing water from circulating through the engine. Replace the thermostat and test the engine to see if the water flow has been restored.
Reason 5: Cooling system leak
Check for any leaks in the cooling system that may be preventing water from circulating through the engine. Repair any leaks and refill the cooling system with the appropriate coolant.
Before I get to the conclusion you can check my other problematic article – Honda bf225 fuel pump has no power.
Mercury 115 2 Stroke Misfire Problem
The “Mercury 115 2-Stroke Misfire Problem” is a common issue that boat owners with Mercury 115 2-stroke engines may encounter. It refers to a situation where the engine does not run smoothly and consistently.
| Reason | Solution |
|---|---|
| Ignition Issues | Ensure all components in the ignition system are in good working condition and replace faulty parts. |
| Stator and Trigger Problems | If the stator or trigger is faulty, consider replacing them to ensure proper engine firing. |
| Fuel System Blockages | Clean or replace the fuel filter and carburetor, or use fresh fuel to ensure a clean fuel supply. |
| Low Compression | Diagnose and address the root cause, such as worn piston rings or a damaged cylinder head. |
Reason 1: Ignition Issues
Sometimes, even if you’ve changed spark plugs and coils, there might still be problems with the ignition system. This is like the engine’s “spark” not working correctly. You should check it and make sure everything in the ignition system is working as it should.
Ensure that all components in the ignition system are in good working condition and replace any faulty parts.
Reason 2: Stator and Trigger Problems
If the stator or trigger is not working right, it can make the engine run rough. These are important parts that help the engine know when to fire. If they’re not working, it can cause trouble. If the stator or trigger is faulty, consider replacing them to ensure proper engine firing.
Reason 3: Fuel System Blockages
If there’s a clog in the fuel filter, the carburetor is dirty, or you’re using old fuel, it can lead to a misfire. Clean or replace the fuel filter, and carburetor, or use fresh fuel to ensure a clean fuel supply to the engine.
Reason 4: Low Compression
If one or more cylinders don’t have enough compression it can cause a misfire. f compression is low, diagnose and address the root cause, such as worn piston rings or a damaged cylinder head. and then replace the piston ring or cylinder head as necessary.
Reason 5: Reed Valves Not Sealing
Reed valves are like doors in the engine that need to close properly. If they don’t close well, especially at low speeds, it can cause a misfire. Check and replace reed valves if they are not sealing properly to maintain proper engine performance, especially at low speeds.
115 2 Stroke Mercury outboard motor won’t get past 3000 RPM
Sometimes, your 115 2-Stroke Mercury outboard motor can face difficulty achieving higher speeds or power output and become unable to reach or exceed 3000 RPM.
| Reason | Solution |
|---|---|
| Fuel System Issues | Use good quality fuel, clean or replace the fuel filter, replace the fuel hose if needed, and check/test the fuel pump. |
| Propeller Problems | Check the propeller for damage or obstructions, and replace it with the correct type if necessary. |
| Low Cylinder Compression | Test the cylinder compression and address issues with piston rings or the cylinder head. |
| Ignition System Trouble | Check and replace malfunctioning components like spark plugs, coils, CDI, stator, or trigger. |
| Impeller Issues | Inspect the impeller and replace it if it’s not functioning correctly to ensure proper cooling. |
Reason 1: Fuel System Issues
If you’re not using good quality fuel or if the fuel filter is clogged, it can restrict fuel flow. Also, check for kinks in the fuel line and replace it if needed. A faulty fuel pump can be a problem too, so test and replace it if necessary. Make sure the engine gets the right fuel. Use good fuel, clean or replace the fuel filter, replace the fuel hose if needed, and check/test the fuel pump.
Reason 2: Propeller Problems
The propeller plays a big role in how the outboard motor performs. If it’s the wrong type, has debris on it, or is damaged, it can limit the engine’s power. Check the propeller for damage or obstructions, and replace it if necessary with the correct type.
Reason 3: Low Cylinder Compression
If the engine’s cylinders don’t have enough power, it can struggle to reach higher RPMs.Solution: Test the cylinder compression and fix any issues with piston rings or the cylinder head.
Reason 4: Ignition System Trouble
A faulty ignition system can make the engine run rough and have trouble reaching higher RPMs. You should check and replace any malfunctioning components like spark plugs, coils, CDI, stator, or trigger. Test and replace any faulty ignition system components.
Reason 5: Impeller Issues
The impeller is responsible for moving water to cool the engine. If it’s not working right, the engine can overheat and lose power. Inspect the impeller and replace it if it’s not functioning correctly.
Final Tip
It’s all about the Mercury 115 2 stroke problems. Here are some final suggestions for you
It’s important to diagnose and address the root cause of the issue to prevent further damage to the engine. If you’re not comfortable working on your outboard engine or if you’re unsure about the cause of the problem, it’s always best to consult with a qualified mechanic or technician for assistance.
