8 Symptoms To Detect A Faulty VST Filter On Yamaha Outboard

Imagine you’re hurling through the river on your boat, and the engine starts misfiring. You notice a steady deceleration even with full throttle. The situation gets worse as soon as the engine stops completely. 

These all can happen due to a clogged VST filter. To avoid the consequences, you must look for symptoms. The typical symptoms include misfiring, increased fuel burning, zero pick-ups at higher RPM, and complete power loss. All these issues can be avoided if you take swift action based on the symptoms. 

In this article, we will describe every bit of detail about Yamaha VST filter symptoms, the reasons behind the issue, and how you can fix them. We will also talk about the cost of replacing the VST filter.

8 Signs of a Clogged Yamaha Outboard VST Filter

There are several major and minor Yamaha VST filter symptoms to look for. While some of them might seem to be unrelated, they all indicate issues with the VST filter. Here’s a list of the most visible ones.

Symptom 1: Engine Sputter Noise

The most prominent problem with a clogged VST filter is the sputtering noise. You will hear a steady sputter whenever you fire up the engine. The problem will only deepen depending on the level of clogging. 

The sputtering on the engine is caused by clogging. The sputtering is a sign of bad fuel and fuel stabilizers. So make sure you use quality fuel for filter longevity. 

Symptom 2: Difficulty in Starting the Engine

Whenever you try to start the outboard engine, it shows an error message. Now, this is something that isn’t always the VST filter’s fault. 

There is a high chance that other electrical components like sparks, plugs, or the battery might be faulty. 

So rather than jumping straight to VST filter replacement, check the electrical components first. If those are fine, consider replacing the filter, as it may block the fuel flow. 

Symptom 3: Idling Issues

Another telltale sign of a clogged VST filter is the idling issue on the outboard motor. You may start the engine and let it run for a while before it abruptly stops due to an idling problem. 

Generally, the idling issues occur when the VST filter is older than 250 working hours on the motor. 

So, if you have a long-running motor, now might be the time to change the VST filter. You can check running hours from the dashboard. We strongly suggest checking the running time.

Symptom 4: Engine Efficiency Reduced

Every outboard motor has a specific output efficiency level. If the VST filter is clogged, you will see a reduced efficiency on the engine. 

Moreover, it will also tend to work erratically with hesitations and stutters every time you travel with a full load. 

The efficiency is almost always exclusively caused by a worn-out VST filter. You should either clean or replace it. 

Symptom 5: Erratic Start Sequence

A completely clogged VST filter will prevent the fuel flow to the engine. In that case, the engine will not start at all. 

But if it is unclean or has been running over the 250-hour mark, you may notice an erratic start sequence as the fuel inflow becomes unpredictable. 

You will see that sometimes the engine starts as usual and other times it completely fails. The only solution here is to replace the VST filter. 

Symptom 6: Engine Stalling

This is another common sign of a clogged VST filter. If you notice that your engine drastically stops as you take a turn, it might be that your engine is stalling because of VST filter clogging. 

The engine may start on its own again if the fuel line is not completely blocked. In the long run, continued engine stalling will hamper your acceleration mechanism and wear out the engine. 

Symptom 7: Fuel Line Component Issues

A clogged VST filter may also often cause fuel line component issues. A lack of proper flow will cause the line and the fuel motor to overwork which may lead to spillage and leakage. 

The problem becomes even more severe if it’s a complete clog rather than a partial one. 

Symptom 8: High Vacuum Gauge Reading

Another clear sign of a VST filter issue is the high vacuum gauge reading on your dashboard. When the VST filter is clogged, it will inevitably create a vacuum on the fuel line. 

This vacuum will show up on the gauge reading. So if the gauge reading is high, you know what to do. 

Possible Causes of a Clogged VST Filter on Yamaha Outboard

Well, you know all the symptoms that point to the clogged VST filter. Now let’s look at what causes the VST filter to clog on the Yamaha outboard.

• Bad fuel quality 
• Microbial growth
• Sludge growth 
• Condensation leading to secondary growth 
• Metallic fragments on the fuel line 

Replacement And Repair Costs of Clogged VST filter on Yamaha Outboard

The cost depends on many factors. While replacing the VST filter, you will also need to replace the vaporization tank on top of the VST filter.  

Anyway, the filter or gasket cost shouldn’t worry you. It’s the repair cost that should be your headache.

 You can always replace them on your own if you have basic technical knowledge, but leaving it to the experts is better. Here’s a price breakdown. 

Criteria	Price
VST Filter	30 dollars
Vaporization tank	25 dollars
Repair cost	Around 600 dollars

Tips For Maintaining the Yamaha VST Filter To Prevent Future Failures

Here are some quick tips for maintaining your VST filter to prevent future failures. 

• Ensure there’s no water leakage into the fuel tank 
• Use high-quality fuel 
• Take out and clean the VST filter as soon as you see vacuum build up on the gauge 

Frequently Asked Questions

Now that you know everything there is about the Yamaha Outboard VST filter clogging, let’s look at some of the common questions asked by the users.

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