6 Symptoms of A Bad Fuel Water Separator: Causes, Fixing Cost, Tips, and More!

When you’re on a roll, your boat engine is eating up the fuel just as Don Gorske would eat hundreds of hamburgers in no time. The fuel system carries out this massive task. A fuel water separator is part of this fuel system that prevents the water from getting into the fuel tank.  

After a specific time of water trapping, your fuel-water separator will be full or show signs of deterioration due to the accumulation of water, debris, etc. This causes corrosion of the separator unit and the whole fuel system gradually. 

Anyway, No need to worry; we are here to answer common questions and clear any doubts regarding your defective fuel-water separator. Binge on to know the details!

What are the Symptoms of A Bad Fuel Water Separator?

Basic symptoms of a bad fuel water separator are low engine power, stuttering, poor acceleration, and a few others that we’ll now discuss in detail. Let’s see.

Symptom 1: Power Down When Under Load

While the engine isn’t functioning or stalled, a lower fuel supply rate will permit adequate fuel pressure. 

When it comes to increasing the load on the engine or acceleration of the vehicle, the fuel demand increases drastically. 

A clogged fuel water separator allows the flow of water into the fuel system, corroding the system and hence powering the engine. 

Symptom 2: Difficulty in Starting the Engine

The primary mechanism behind starting your vehicle when the key is turned on is as such- the fuel pump efficiently works to supply oil to the supply line forcefully.

However, a lousy water separator will prevent it from generating such fuel pressure with unexpected water passage. 

And with no fuel to keep the engine going, your vehicle will not start or may start for a couple of seconds.

Besides, the engine will also emit white and black smoke during the starting process or when running.

Symptom 3: Poor Engine Power

A clogged fuel-water separator will eventually cause an overall loss of engine power, especially during acceleration. 

To help guard the vehicle against potential engine damages, the engine control unit will restrict any result. 

As a result, the vehicle may sit inactively, enter limp mode, and eventually show poor engine power.

Symptom 4: Carbon Deposits

When your boat has a bad fuel water separator, the debris and water will enter the fuel filter. 

As a result, carbon deposits will also occur in the intake duct, intake valve, and cylinder. 

This leads to issues like trouble in engine start, low acceleration, and heating up of the engine, all leading to engine damage. 

Symptom 5: White Smoke Generation

A common symptom indicating a bad fuel-water separator is white smoke coming from it. 

This happens when the water is burned or extremely heated, generating white smoke. 

The emitting water vapor damages the fuel injectors, reducing engine power and finally causing engine damage.

Symptom 6: Damaged Fuel Pump

Due to the insufficient fuel supply due to the clogged water separator, the fuel pump has to retain a heavy load. 

Besides, as the water vapor damages the fuel injectors, the fuel pump will eventually be affected.

Although it might work just fine under pressure initially, it will eventually show signs of giving up.

Of course, changing the fuel water separator sooner is better than changing the whole fuel pump or the system. 

4 Possible Causes of Fuel Water Separator Failure On A Outboard

Fuel water separator failure on the outboard motor of boats is a common problem. Although you know the symptoms of a bad fuel water separator by now, the possible causes are still unknown. And so, here they are- 

Water Entrance

In the case of an outboard motor, the water entrance is the primary reason for a fuel water separator. 

Water enters the fuel system from several sources, such as condensation, fuel tank leakage, or even rain. 

The fuel water separator acts as a filter, trapping any water in the fuel and removing it before it gets to the engine. 

With a clogged separator, the engine runs poorly or may even fail to start, as aforementioned. 

Clogged Filter

A clogged filter is another reason behind your failed fuel water separator. The fuel filter prevents dirt and debris from entering the fuel system, but over time, it gets clogged. 

If the fuel filter is not replaced regularly, it causes blocking of the separator, eventually preventing it from separating the water.

Fuel Leakage

The fuel water separator also damages due to fuel leakage. Fuel may leak from the fuel lines, fuel tank, or carburetor. And if it is not identified in time, it can erode the separator and cause it to fail.

Deposits and Moisture

Decaying steel fuel lines, fittings, and tanks get rusted with moisture. Besides, poor-quality fuel comes with a large quantity of sediment. 

Again, silt deposits from in-ground storage tanks at filling stations and moisture are all responsible for a failed fuel water separator. 

Replacement and Repair Costs of Outboard Bad Fuel Water Separator

Undoubtedly, fuel water separators are an essential part of any outboard motor. And when the fuel water separator quits, that’s a headache for the boat owner. But don’t worry, the replacement, repair, or maintenance costs aren’t as high.

Replacement Costs:

It depends mainly on the make and model of the outboard motor. Generally, the cost can vary from as little as $130 to several hundred dollars for a brand-new fuel filter water separator. 

To get an accurate cost estimation, it is essential to contact the manufacturer or a local outboard motor repair shop. 

Repair Costs:

When it comes to repairing the damage, the cost depends on the severity of the damage. Simple repairs, such as replacing a clogged filter, can cost as little as $50. 

However, with more significant damage, the price hikes, such as replacing a damaged gasket or seal, can cost up to $100 or even more. Besides, the labor cost can range from $60 to $90. 

Before attempting any repairs on your own, it is wiser to consult a qualified outboard mechanic. 

Maintenance Costs:

Routine maintenance on your outboard motor’s fuel water separator helps prevent costly repairs and replacements. 

Simply cleaning the filter every season or after every 100 hours of operation can extend the separator’s life or even the motor’s life for months. The cleaning cost can be as little as $5 to $10. 

Tips for Maintaining the Outboard Fuel Water Separator to Prevent Future Failure

Since regular maintenance allows you to take a break from spending hundreds and thousands on repair and replacement, it’s always a better option. Here are some tips to save you a good deal of money-

Check the water separator for replacement

Depending on the type of engine and the amount of use, it is suggested that you replace it every 25-100 hours of operation. 

Hose inspection

Inspect the hoses that connect the fuel water separator to the engine and fuel lines. Look for signs of splitting, cracking, wear and tear, and replace the hoses immediately if they show damage. 

Regular cleaning

Keep the fuel tank clean by draining any sediment or debris that builds up over time. This will prevent clogging and contamination of the fuel water separator. 

Check the water level

Ensure the water level is below the ‘full’ mark on the side of the separator. If the level is too high, it could result in the poor engine functioning.

Bleed out the fuel system

Drain the fuel system after replacing the filter element or anytime the fuel system is opened. This ensures that all the air is removed from the system and that the fuel flows freely. 


Apart from the above discussion, questions might wander in your head; let’s see if we can answer them.

How do I know if my fuel water separator is bad?

The easiest way to know is if your vehicle shows symptoms like engine starting difficulties, white smoke emissions, stuttering, or even poor motor power.

What happens when the fuel water separator is complete?

A fuel water separator implies that water is passing through the fuel systems, which will cause fuel system corrosion and eventually failure.

How long does a water fuel separator last?

Fuel water separators last about a year or so. Hence, replacing it every year or after about 25-100 hours of use is recommended. 

Can you drain the fuel water separator while running?

No! Draining the fuel water separator while the motor’s running isn’t only hazardous for the vehicle and the passengers or driver.

Similar Posts