What Does A Boat Blower Do? (Explained)

What Is A Bilge Blower Used For?

A bilge blower (not to be confused with bilge pump) is a very important part of your boat, not only because the United States Coast Guard (USCG) may require it, but because it can also save you life!

Ok, so what exactly is this blower and how is it potentially life-saving?

 Well, let’s get right into it…

If you have a boat that has a covered engine compartment like the inboard outboard setup, you will need to use the bilge blower before starting your engine to expel any and all highly flammable fumes from the engine compartment. 

How Long Should You Run Your Boat’s Bilge Blower Before Starting Your Gasoline Engine?

After doing extensive research…because I’m not claiming to be an expert, but rather, I want to make sure I am doing what is necessary myself keep my family and passengers safe.

It is recommended that you run the blower for at least 4-5 minutes before starting the engine... I must admit haven’t always done this in the past. However, with my family to protect, I now always kick that blower on before I approach down the launch ramp and make sure I let it run for the full 4-5 minutes before starting the engine.

Now, when we’re camping and have our boat slip, I will simply run the blower as a family is getting the stuff together and piling into the boat again making sure that I run this for recommended 4-5 minutes making sure all the potential gas fumes are out.

How Often To Run?

Make it part of your routine every time before you start your engine so you’re not taking any chances of blowing your engine cover off… or something even worse.

Full recommended safety procedure:

  1. Run blower for at least 4 minutes.
  2. Then do a sniff test in the engine compartment for an odor of gasoline vapors.
  3. Run blower while the engine is at idle or under wake speeds.

I have heard too many horror stories about boats catching fire or exploding…scary stuff! 

But you just need to take the appropriate safety precautions to ensure you don’t have an accident that could have been prevented.

After doing hours of research, I do believe most people…including myself,  run the blower all the time.

 If the engine is running then the blowers are running. I know if the boat is on a plane then it should be drawing in fresh air but because I have forgotten to turn it back on after slowing down to idle, I feel it is the safest to simply keep it running all the time.

When pulling skiers and tubers you don’t have to remember to turn it on and off when you are getting them in and out of the water.

 So for me…I have decided to run mine at all times to eliminate the problem of forgetting.

Also, DONT run the blower while fueling up the boat from the water. This can actually draw in fumes to your bilge as your pumping your gas. Rather, it is recommended to run only after you have completed the filing.

After you are done pumping the case, smell around the engine compartment and the blower to make sure they are doing what there supposed to be doing.

Don’t underestimate the stiff test…

It would be recommended to open the engine cover after fueling just to make sure nothing is trapped in the enclosed compartment.

Remember… if you have a fuel leak, then running the blower is only hiding a potentially serious issue that needs to be addressed ASAP.

What Type Of Bilge Blowers Are Available?


The most common design is called an in-line bilge blower and my 20’ open bow has 2 of them. Both are located in the stern of the boat, one on the port side and the other on the starboard side.

I use and recommend ones rated for continuous duty bilge blower.


You can find quiet bilge blowers but only to a certain extent… but remember these things need to move a lot of air and are usually  3in or 4in diameter. So the noise level can only be so low. 

The good news is when the boat is running I have noticed I don’t even hear them running and notice them only when the boat is turned off.

How Many Bilge Blowers Do I Need?

 As I mentioned earlier in this article I have two on my personal boat which is pretty standard. It’s standard because you want to have one on each side drawing in the fresh air and expelling any possible fumes.

 It would be recommended if you only have one, to buy the second one making are they are cycling fresh air into the engine compartment to prevent any fume build-up.

Proper Bilge Venting 

Another piece of this system is the bilge blower hose which is similar to a hose you would find on your dryer at your house.

They’re positioned at the bottom of the bilge area to get rid of any gasoline fumes. They’re placed at the lowest point because gas fumes are heavier than air and will sink down to the lowest part of the engine compartment. Because of this, you should make sure the opening of the hose is as low in the bilge as possible.

Bilge Blower Maintenance

You should regularly check your bilge blower setup making sure there is nothing leaking or items not secured properly.

Here are the parts that make up the airflow system that should be inspected from time to time.

  • Bilge blower-Check the blowers to ensure they are running and not just making noise. They can break and if not inspected you might not notice that they are not moving air as they should.
  • Blower hose- Make sure the hoses are not bridled or have holes in them. If you notice these things, replace imminently with a new hose.
  • Support points- Check and make sure your bilge blowers are firmly secured and the hoses are routed properly and secured without any kinks. 

Final thoughts

I personally like to be safe rather than sorry…especially when it comes to my family. That is why I choose to run my blower constantly when my boat engine is running. Now I know others may disagree and that’s okay.

I also encourage boaters to do an inspection on your boat of all parts that may wear out over time but especially the blowers and other parts that make up that system as listed about. 

I hope you found this article was helpful and as always be safe and happy boating!

Project “Safety First” Boating

Check out our article on: What Should You Do Before Fueling Your Boat? (Important!)

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Project Boating Editorial Staff

My name is Brad Visser the chief editor and owner of Projectboaing.com. We have an amazing team of writers that contribute to our website. This team is passionate about boating and have years of experience not only in boats, but in writing helpful, informative articles to answer questions you may have.

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