5 Symptoms To Detect A Bad Primer Bulb On An Outboard

The primer bulb is a crucial component of any outboard; it is responsible for drawing fuel inside the engine. So, when the primer bulb goes bad, you will have a tough time starting your outboard correctly, which can be very annoying.

But, luckily you do not need to open up your whole outboard to check if the primer bulb has gone bad. Instead, you can look for symptoms of a bad primer bulb, and you can easily understand the condition of your primer bulb.

So, today in this guide, we will discuss all the symptoms that will help you detect a faulty primer bulb.

What Are the Symptoms Of A Bad Primer Bulb On An Outboard Motor?

When the engine is cold-started, the priming bulb in the fuel line connecting the fuel tank and the engine is used to fill the engine with fuel. 

Thus, when it goes bad, you need to fix it to quickly identify a faulty primer bulb using the symptoms listed below.

Symptom 1: Primer Bulb is Too Soft

One of the key symptoms of a bad primer bulb is the bulb will be too soft and not become hard. 

Generally, a primer bulb is designed to pull gasoline from the tank whenever you press it. 

It should remain hard till the engine float closes and prevents the fuel injection system from receiving the feed. It should stay like this until the engine fires up and operates for a time.

The priming bulb won’t become hard when it deteriorates; instead, it will continue to be soft. This often occurs when a fuel line leak causes pressure to drop.

Symptom 2: Primer Bulb Doesn’t Pop Up

If you drive an outboard regularly, you know how a primer bulb works. It should pop up whenever you push the primer bulb, showing that the carburetor has got the fuel properly.

However, when the primer bulb has got damaged, it won’t pop up. Moreover, you won’t feel any resistance while attempting to press a damaged priming bulb. 

This can also result in additional issues, such as your carburetor becoming flooded with fuel, which can seriously harm other components of your boat.

Symptom 3: Engine Having Hard Start

A fully functional primer bulb is essential for ensuring proper running and starting of your outboard engine. So, the engine will have hard and cold starts when this goes bad. 

Simply push the priming bulb and see how it is while the engine has been off and if it has a sluggish or cold start. 

If you see that the bulb is soft after pushing it, the priming bulb is likely damaged. When your priming bulb is worn out, you will also hear ticking and other strange noises.

Symptom 4: Cracks On the Primer Bulb

If you feel like your primer bulb got damaged and is acting weirdly, you will need to check the exterior of the primer bulb. The bulb can get cracked due to frequent use and wear and tear. 

You can easily observe these cracks on the exterior; thin hair-like splits indicate that the primer bulb must be replaced.

Symptom 5: Leaking Primer Bulb

Another easy-to-detect symptom of a bad primer bulb is fuel leaking. The primer bulb’s body or the locations where the hose is attached to take in or release fuel from the priming bulb can be cut. This cut has the potential to cause leakage.

Replacement And Repair Costs Of Outboard Bad Primer Bulb

The cost of a new primer bulb is relatively inexpensive and readily available on amazon. However, the overall cost will increase if you hire a mechanic to do the work. Here is the estimated cost.

FactorsReplacement CostLabor cost
New primer bulb$12-$30$50-$100
Fuel Line leak$6-$7 per foot for the hose$100-$400
Blocked Primer bulbN/A$50-$100

Additionally, there can be leakages in the fuel line, which can lead to malfunctioning primer bulbs. So, in this case, you do not need to replace the primer bulb; instead, you need to get the fuel line fixed, which can be expensive. 

Additionally, the primer bulb may become clogged; to make it usable again, you can clean it yourself. If you do not want to take the trouble, hire a mechanic.

Tips For Maintaining The Outboard Primer Bulb To Prevent Future Failures

These tips below will help you keep your outboard primer bulb working like new for a long time without any issues.

  • Open and clean the primer bulb once every week 
  • Check the fuel lines at regular intervals for any blockages or leaks
  • Change the primer bulb every 4 years


After reading our guide so far, you can have some questions roaming around your head, and thus below, we will talk about these Frequently asked questions.

When Do I need to change my primer bulb?

Outboard primer bulbs are not meant to work forever. So, generally, if you maintain them well, they should last for around four years and will need replacement after 4 years.

Is it possible to repair a bad primer bulb?

Repairing a primer bulb in most situations is impossible. Therefore, you will need to replace it with a new one. However, sometimes it can get blocked due to dust, which can be easily cleaned, and you can reuse the primer bulb.

Why is my outboard primer bulb losing its prime?

There are two major causes: a fuel pump control valve leakage or an air leak before the primer bulb. Typically, this problem is brought on by a leaky fuel system link at the tank or any connections before the priming bulb.

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