Mercury Outboard Alarm Stays On – 5 Causes!

If you are a Mercury outboard engine boat user, you must know how frustrating it is when the Mercury outboard alarm stays on. It is one of the common problems that most boat owners encounter which could indicate various issues with the engine. 

In this article, I will identify and address some of the frequent causes behind the “alarm stays on” problem and suggest appropriate solutions. So, stay with us till the end.

Mercury Outboard Alarm Stays on a Quick Review

As I’ve said, in this blog, I will discuss the common issues that cause the Mercury Outboard alarm to keep beeping. Before we head toward the descriptive discussion, let’s have a quick review of the issues and their solutions.

Engine OverheatCheck water intake for debris or obstructions.
Low Oil WarningTop up the oil reservoir with the recommended oil type.
Loose Remote Oil Tank CapsEnsure remote oil tank caps are tightly closed and sealed.
Loose Hoses on the Oil System LinesInspect and tighten all oil system hose connections.
Low Engine Oil Reservoir LevelRegularly check and top up the engine oil reservoir.

Before we start, let’s check 0000 if you have a few minutes to spare.

Reason 1: Engine Overheat

When the Mercury outboard engine overheats, it can lead to serious damage if not addressed promptly. Overheating may occur due to several reasons, such as a lack of proper cooling or a malfunction in the cooling system.


  • Continuous alarm beeping.
  • Engine temperature gauge reading higher than normal.
  • Reduced engine performance or stalling.


  • Insufficient water flow through the cooling system.
  • Malfunctioning thermostat.
  • Clogged water intake.
  • Impeller damage.


  • Immediately turn off the engine if the overheating alarm is triggered. Let it cool down before attempting any further checks.
  • Inspect the water intake for debris or obstructions that may be hindering proper water flow.
  • Check the impeller for signs of damage, wear, or blockage. Replace if necessary.
  • Verify the thermostat’s functionality, replacing it if it is not opening as it should.
  • Regularly maintain the cooling system by flushing it with fresh water after every use and replacing the impeller as per the manufacturer’s recommendation.

Reason 2: Low Oil Warning

A low oil warning alarm indicates a potential issue with the oil level in the engine’s reservoir. Insufficient oil can lead to increased friction, damaging engine components over time.


  • Continuous alarm beeping.
  • Low oil level in the oil reservoir.
  • Potential smoke or unusual engine noise.


  • Oil leaks or seepage.
  • Oil consumption over time.
  • Faulty oil level sensor.


  • Check the oil reservoir for any signs of leaks or damage, addressing the issue immediately.
  • Top up the oil reservoir with the recommended oil type if the level is low, ensuring it is at the appropriate level.
  • Monitor oil consumption regularly and perform timely oil changes to maintain proper levels.
  • If the alarm persists despite appropriate oil levels, have the oil level sensor checked or replaced by a professional.

Reason 3: Loose Remote Oil Tank Caps

The remote oil tank stores oil for the two-stroke oil injection system. Loose or improperly sealed oil tank caps can cause the alarm to go off as the oil may not be delivered adequately to the engine.


  • Intermittent or continuous alarm beeping.
  • Oil smell around the engine area.
  • Visible oil leakage.


  • Caps were not secured tightly during the last oil refill.
  • Worn-out or damaged O-rings on the caps.


  • Ensure the remote oil tank caps are tightly closed and properly sealed after every oil refill.
  • Check the condition of the O-rings and replace them if they appear damaged or worn out.
  • Clean any spilled oil around the tank and engine to avoid potential fire hazards.

Reason 4: Loose Hoses on the Oil System Lines

The oil system in the Mercury outboard engine includes hoses that transport oil from the remote tank to the engine. Loose or disconnected hoses can disrupt the oil supply and trigger the alarm.


  • Continuous alarm beeping.
  • The smell of oil around the engine area.
  • Visible oil leakage.


  • Hoses are not properly secured during maintenance or repairs.
  • Cracked or damaged hoses.


  • Inspect all oil system hoses for secure connections and any signs of damage.
  • Tighten any loose connections, ensuring a snug fit.
  • Replace hoses that show signs of wear, cracks, or damage.
  • Regularly inspect the hoses during maintenance and service intervals to avoid potential issues.

Reason 5: Low Engine Oil Reservoir Level

The engine’s oil reservoir needs to be adequately filled to ensure proper lubrication and functioning of the outboard motor. A low oil level can activate the alarm.


  • Continuous alarm beeping.
  • Low oil level in the engine’s oil reservoir.
  • Potential smoke or unusual engine noise.


  • Neglected oil level checks and top-ups.
  • Oil consumption over time.


  • Check the engine oil reservoir regularly and top it up with the recommended oil type as needed.
  • Perform timely oil changes to maintain the appropriate oil level.
  • Monitor oil consumption and address any unusual drops in oil level promptly.

How to Reset Mercury Outboard Alarm 

If none of the above tricks work, you might need to reset your Mercury outboard alarm. The alarm on an outboard motor typically indicates an issue that needs attention. So, it’s essential to diagnose and address the underlying problem after resetting the alarm. 

Here are the steps to follow to reset the mercury outboard alarm

Step 1: Identify the type of alarm

Mercury outboard motors have various alarm types, such as overheating, low oil, low battery voltage, oil pressure, etc. The method to reset the alarm may differ depending on the specific alarm type.

Step 2: Turn off the engine

If the alarm is currently sounding, turn off the engine immediately to prevent any further damage.

Step 3: Address the issue

Before resetting the alarm, you should investigate the cause of the alarm triggering. Common issues may include low oil levels, overheating due to cooling system problems, or low battery voltage. Inspect the motor and resolve the problem if possible.

Step 4: Disconnect the battery

If you can’t find any apparent issues or if the alarm persists after addressing the problem, you can try resetting the alarm by disconnecting the battery. This action will reset the system, similar to a computer reboot.

Step 5: Reconnect the battery

After a few minutes (about 5-10 minutes), reconnect the battery to the outboard motor.

Step 6: Start the engine

Once the battery is reconnected, start the engine and check if the alarm is still sounding. If the issue was resolved, the alarm should no longer be triggered.

Step 7: Consult the manual

If the alarm continues to sound even after following these steps, it’s best to refer to your Mercury outboard motor’s user manual for specific instructions on how to reset the alarm or to troubleshoot the problem further. 

The manual will have detailed information about the various alarm types and how to resolve them.

How to Replace Mercury Outboard Alarm Module

Sometimes, resetting the outboard alem also can’t help. In such a case, you might need to replace the module. Want to do that all by yourself? Then, follow the steps below:

Step 1: Disconnect the battery

Before starting any work on the outboard motor, disconnect the battery to ensure your safety and avoid electrical accidents.

Step 2: Locate the alarm module

The alarm module is usually located in the engine compartment or control box, depending on the model and year of the outboard motor. Refer to your motor’s service manual to find the exact location.

Step 3: Remove the old alarm module

Once you’ve located the alarm module, carefully disconnect any wires or connectors attached to it. Take note of their positions to make reinstallation easier later. Remove any mounting screws or bolts securing the alarm module in place and carefully take it out.

Step 4: Install the new alarm module

Place the new alarm module in the same position where the old one was removed. Make sure it’s securely seated and aligned correctly. Reattach any wires or connectors to their respective terminals according to the notes you made during disassembly.

Step 5: Secure the new alarm module

Use the appropriate screws or bolts to secure the new alarm module in place. Ensure it is firmly attached and won’t move or vibrate excessively during operation.

Step 6: Reconnect the battery

Once the alarm module is installed and secure, reconnect the battery to the outboard motor.

Step 7: Test the alarm

Start the engine and run it to test the new alarm module. Verify that the alarm system is functioning correctly and that it triggers appropriately if any issues are detected (e.g., low oil pressure, high engine temperature, etc.).

Step 8: Double-check

After the installation and testing, perform a final inspection to ensure that all connections are secure, there are no loose wires, and everything is functioning correctly.

Remember, this is a general guide, and the specific steps and procedures may vary depending on the model and year of your Mercury outboard motor. 

A Mercury outboard alarm that stays on can be indicative of various underlying issues. As a responsible boat owner, you should find out the problems promptly and perform regular maintenance to ensure the smooth and reliable performance of your outboard motor.

Well, if you have some time left, please check Mercury 40 HP 2 Stroke Problems.

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