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Unblocking Outboard Carburetor Jets

In this video I show a quick trick for unblocking a carburetor jet in the field. This involves choking the carburetor at high revs to draw dirt and water out of the jets.

Unblocking Outboard Carburetor Jets – Video Transcript

Hey there Dangar Stu here. Today's video is a quick tip on cleaning out carburetors and is proudly sponsored by MarineEngine.com.

So, these particular techniques have been around forever used a lot on cars, boats, bikes, whatever but it's actually really handy in some circumstances. It's certainly no substitute for taking a carburetor apart and cleaning it properly but if you're sort of stuck out of the water and you want to give it a try it might get you going again.

Before I show you using this technique I'll just draw a quick diagram on the board to go through the theory just really quickly. Here's a sort of simplified diagram of carburetor. So, this is the front where air comes in, then you've got your fuel bowl here and your jets where the fuel comes through and your butterfly valve the throttle plate here and going into the engine here. So, the idea is as the piston goes down it draws air in through the throat of the carburetor. Then because it's got this venturi shape to it the air actually accelerates and it becomes slightly lower pressure and that's what causes the fuel to be sucked up through the jets and in the air & fuel mixture goes into the engine.

When we accelerate the motor so, we lift the fast idle on the motor this throttle plate opens a little bit air comes through and a proportional amount of fuel gets drawn up through the jets. Now if those jets are blocked obviously, you start running a bit lean you're not getting enough fuel. All we do with this technique as you'll see in a moment is lift the fast idle, get the rpms up a little bit, then I just take a rag and hold it in front of the carburetor completely choked it off. Once we got the rag over the front of the carburetors the piston goes down it tries to draw air in through the carburetor and because it's blocked off it creates a really strong vacuum inside the carburetor. And this vacuum then pulls a lot of fuel through but hopefully will also pull a droplet of water if it's blocking the jet or a little bit of dirt or something like that.

So, it can just be a really quick way to try and clear a carburetor jet. If you actually have a mechanical choke on the carburetor you can just try gain the ribs up and pulling that choked out and blocking it off. Chokes generally don't close a cover to completely they'll help a lot and you might find it's all you need to do. But a lot of modern engines don't have chokes anymore they've got these sort of prime start enrichment systems that are great for adding more fuel to start. But they are actually functioning as chokes. I think this works a little bit better with multi cylinder engines because you've got one cylinder working normally to keep the motor running. Whereas if you've got a single cylinder motor as soon as you do this choking you it will die and stall pretty quickly but it still can be used.

All right we'll take a look at this technique in action now. Hopefully you could see on camera then that quad on the fuel comes out and a throw to the carburetor particularly with the motor tilted up a little bit. So be careful with that you obviously don't want to start a fire but it does go to show how much that vacuum just pulls fuel and dirt out through the carburetor jets.

Alright, well that's all for today just a quick tip that might help you down the track if ever you're sort of stuck out on the water and you can't take the carburetor and clean it properly. It's certainly no substitute for a proper carburetor clean but it might just get you out of trouble one day. All right well take care I'll catch you soon.