Most Common Problems with Boat Gas Tank Vent

One of the most important parts of a boat is a gas tank vent. If you don’t want your boat getting a vacuum block, make sure you have a healthy gas tank vent. 

The gas tank vent exists outside the boat near the fill port. It’s important to have the vent open when operating the motor. 

As an important device, people report facing some common issues with it. Today I will discuss the most common problems with boat gas tank vents and possible solutions. Read till the end to find out! 

A Quick Overview to Boat Gas Tank Vent Issues and The Reasons Behind Them:

Fuel Spillage.Fuel Backs Up to the Motor. from Pump.Fuel Tank Vent Clogged.Fuel Vent Line Clogged.Clogging at Fuel Tank Fitting.Air Locking.Clogging of Venting Regulator. 
Boat Dies.Primer Bulb Collapses.Fuel Line Restriction.Vent Restriction.Checkball Sticking.A Defective Anti-Siphon Valve. 

1. Fuel Spillage/Fuel Backing Up

The boat seems to refuse to take fuel. When trying to put fuel, the fuel overflows. It needs squeezing fuel in small amounts to refill. That means putting in small amounts of fuel at once. 

It is embarrassing. Because it takes forever to refill just 1 gallon. It does more than creating a few frowns at the gas station. Air locking usually cuts off the filling pump nozzle.

Reason for the Problem:

You can call a vent clogged when it is not allowing a free flow of air. Sometimes, the vent can be broken or corroded. It can even be upside down. Which causes the blockage of the gas tank vent. 

A more surprising find is an absent vent. Moreover, salt and dirt collect on vents with screens.. Sometimes the hole of the vent is faced upside. This may let rainwater enter it along with other things. This can cause the clogging of the vent.

However, if the vent seems okay, check for the vent pipe or hose next. A kinked vent hose obstructs the vent. The way the hose is fashioned is also a big deal. It should form a loop up from the vent and then go down as a loop. It also should come upward from the vent fitting.

The fitting of the vent is the problem when both of the above are okay. A right-angled (90 degree) barb on a screw-in fitting can have clogged dirt. 

Air locking is vapor trapped in the vent hose. This air blocks fuel from passing to the pump. Air locking is the reason why the fuel doesn’t seem to enter. Or, fuel may enter very slow. 

In some boats, a venting regulator is installed. Sometimes the regulator clogs due to dirt. That obstructs the fuel flow and overflow occurs. 

Possible Solution:

The vent clog needs to be cleared. On the other hand, a kinked hose needs to be fixed. The tank fitting needs to be fixed as well if that is the problem. Fixing these issues will relieve any air locking as well. Cleaning the venting regulator if it exists will stop the overflowing situation too. This should also resolve the fuel backing up situation as well. 

To fix this:

Things You Will Need:

  • Screw Driver.
  • Brush.
  • Warm Water.
  • Flashlight.
  • Mirror.

Troubleshoot 1: Clear Clogged Vent

Inspect the vent from the outside. Remove a corroded vent. Replace it with a new one. 

If the vent contains a screen, then take it off. Unscrew it and clean the screen of any clogging. Try gentle swiping motion for the dusting. Use warm water to clean salt and dirt. 

Fix the position of the exhaust hole. If it’s up, then turn it so that it faces down. 

Troubleshoot 2: Clear Clogged Vent Line

Fix the loop position if the hose is not looped correctly. Disconnect the hose from the pump and dry out if there is any water. 

If there is a kink in the vent, then fix the kink. To find the kink, use a mirror and flashlight. 

Troubleshoot 3: Clear Fuel Tank Fitting 

Unscrew the fitting. Clear any dirt that is clogged with warm water.  

Troubleshoot 4: Clean Venting Regulator

Disconnect the venting regulator. After disconnecting, try filling the pump with fuel. The problem should be fixed. 

Now inspect the regulator. Clean any dust and dirt from the regulator.  

Troubleshoot 5: Getting Rid of the Air Lock

If the kinked hose and clogging are removed, the airlock should go away. Otherwise, disconnect the hose and straighten it. Then set it in the correct position again (loops up from the vent and then goes down as a loop).

2. Boat Dying/ Primer Bulb Collapsing 

Usually, fuel backs up and spills. It happens after some time of filling the fuel tank. Fuel usually spills away from the fuel filler pipe. 

Of course, the usual air escaping sound is absent. Also, the boat may die several times. This interrupts your regular fishing trips.

A broken primer bulb may also be caused by a bad gas tank vent. The prime seems to go away or the bulb collapses in higher RPMs. 

Reason for the Problem:

The primer bulb collapses usually if there is a vent restriction. A fuel line restriction would also explain the symptoms. This restriction should exist right before the primer bulb. 

The fuel backing up reinforces the reason to be a vent problem. 

Another cause can be a sticking check ball. A check ball exists inside the pickup tube assembly. It prevents backflow. 

In many boats, anti-siphon valves exist. They prevent the blowing of air into the tank. If any defects exist, then the same valves can cause fuel to back up. 

Possible Solution:

Fixing the primer bulb, relieving any restriction of the fuel line can help. Also fixing a sticking check ball and defective anti-siphon valves will relieve the issue. 

To fix this:

Things You Will Need:

  • Screw Driver.
  • Brush.
  • Warm Water.
  • Carb Cleaner.
  • Magnet


Troubleshoot 1: Fixing the Primer Bulb

Replacing the broken or collapsed bulb is the solution here. Then re-prime the engine and check if the boat runs without a problem. 

Troubleshoot 2: Removing Any Restrictions

A kinked vent line causes restriction. Removing the kink, fixing the position of the lines should cause proper airflow. Restriction in the vent can be removed by removing the mud collecting there. Dirt and salt should also be removed with warm water. 

Troubleshoot 3: Fix Sticking Check Ball

With a bit of magnet and some carb cleaner, clean away the gunk. This gunk is likely making the check ball stick in the valve. 

Also, try pressurizing air on the valve passage. Be careful not to lose the ball in the process. 

Troubleshoot 4: Fixing Defective Anti-Siphon Valves

Replace the broken anti-siphon valve.

What Majority of the Users Feel About Boat Gas Tank Vent?

Most users face problems related to boat gas tank vents. But most reported that it is comparatively an inexpensive problem to troubleshoot. 

In most cases, replacing the vent and removing the kink of the fill line worked. 

Customers suggest, keeping carb cleaner will come in handy in fixing such issues every time. 


A boat gas tank vent is a necessary part of it. As an essential part, it displays some pretty common problems. However, the solution to those problems is pretty basic. Maintaining regular cleanliness can prevent the issues further.

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