Boat Fuel Vent Location

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Updated on April 2, 2022

Every boat needs a fuel vent for smooth operation whenever its engine is on. Without the boat fuel vent, refueling your gas tank will build up too much pressure and cause engine issues. 

A boat fuel vent runs from the gas tank to a surface area on your boat and promotes airflow. The boat fuel vent acts as a bidirectional valve to prevent tank swelling and sudden engine stops. 

Locating the fuel vent on your boat is essential to maximize your vessel’s smooth operation. That’s why this guide provides relevant details to help you locate your boat’s gas vent with ease. 

Where is My Boat’s Fuel Vent?

Newer boat models usually have their fuel tank vent fitted directly onto its fill hose. The hose will usually run from its filling line sideways and onto your boat’s hull area.

Other boats might vent directly from an opening on the fuel tank and in an angled position upward. Such vent fittings might run towards the front hull end or onto a surface area on your boat. 

How to Check Boat Fuel Tank Vent

Step 1: Fill the gas tank

The best time to check a gas tank vent is during refilling. Place the nozzle of your gas gallon or dispenser into the boat’s filling line. 

Step 2: Inspect the vent for escaping air

Get someone to help you hold the gas nozzle while its filling your boat’s tank. Next, locate the vent valve on your boat.

Air pressure should escape from the fuel tank if the gas tank is almost filled. In other cases, escaping air will be noticeable when your fuel tank is full and after its locked.

No signs of escaping air from this vent might mean it’s clogged or faulty.  

How to Properly Vent a Boat 

Correct boat ventilation isn’t the same with fuel tank venting. Boat ventilation requires air movement into and out of your boat. 

Most boats have separate intake and outlet vents to let air in from its front and out through the rear. Several boats have hatches, cowl vent variants, ventilators, and other air outlets to support proper airflow. 

Common Fuel Tank Venting Problems

Fuel back-up is the most common problem experienced from a blocked fuel tank vent. In this case, pressure built up in the tank will send fuel spilling out of its vent. 

Sometimes, a broken anti-siphon valve might aggravate the spill until pressure is released from a gas tank. 

The primer bulb on a boat will easily die if its gas tank vent is clogged. Usually, this happens when the engine operates at a higher RPM rate which puts immense pressure on its fuel tank. 

Stop-start operation of a boat’s engine is another problem caused by the fuel vent. Air pressure that doesn’t get out of a boat might cause intermittent blips in fuel flow. 

Hampered flow of fuel to a boat’s engine will cause sudden stops during operation. 

How to Fix Boat Fuel Tank Vent Open or Closed

First way to fix boat fuel tank vent: Replace anti-siphon valve

Step 1: Locate the anti-siphon valve 

An anti-siphon valve is usually connected to the part of your gas tank designed to allow air in and out.  

Step 2: Get a replacement 

Most boat models usually have similar anti-siphon valves. Make sure the replacement valve you get fits your tank’s airflow valve. 

Replacing the faulty anti-siphon valve will prevent fuel back-up and prevent building up of suction in your boat’s gas tank.  

Second way to fix boat fuel tank vent: Replace/reposition the vent 

Step 1: Access the connecting hose of your fuel tank’s vent

Inspect the connecting hose of your fuel tank’s vent for signs of water or dirt buildup. If there are no signs of water, rust or dirt, the vent may be positioned wrongly. 

Step 2: Check the vent’s positioning

The hose on fuel tank vents must be slanted to support easy airflow and discourage air locking. Make sure any screw fittings located around the vent don’t have rust or dirt on them. 

Step 3: Clean or replace the fuel vent

If the connecting hose and other parts of a fuel vent are not broken, it may not need replacing. Clean out the hose with warm water and allow it to dry out under shade. 

Next, inspect the vent further to make sure no dirt or water is trapped in its hose. But if you can afford it, it’s better to get a new fuel vent hose installed onto your gas tank. 

What Happens If a Boat Fuel Tank is Not Vented?

A boat fuel tank that is not vented will cause sudden stops of its vessel’s engine. Blocked fuel vents will cause fuel to stop flowing after a short while.

After the fuel stops flowing, a vacuum or suction will form inside the tank. When the suction forms, it will gradually grow to a point where it exceeds a fuel pump’s pull potential. 

Built-up suction in fuel tanks will cause vessels to fail starting or operate for a few minutes before stopping. Sustained blockage of a gas tank’s vent will lead to visible swelling on its exterior.