Purpose and function of Carburator hose

[Stephen1]

I have a 1988 Evinrude 90, there is a small hose which runs from the bottom of the carb sound cover back under the engine. It may in fact feed back into the carb. Please advise the purpose or function of this hose. It seems to be designed to capture any fuel which could come out of the throat of the carb and possibly feed it back into the carb.,but when and why would gas be expelled out of the throat of the carb? And if that is the case how is the fuel drawn back up into the carb? If that is really where it is going.

 

[petrolhead]

Re: Purpose and function of Carburator hose

I'm not familiar with your particular motor, but this sounds like the hose that takes excess fuel that collects in the crankcase and feeds it back into the carb. In the old days this excess fuel was simply dumped out with the exhaust, but to comply with modern emissions regulations it has to be fed back in and burned.

 

[Stephen1]

Re: Purpose and function of Carburator hose

To clarify, the hose originates at the bottom of the carb cover housing, not at the crankcase.

 

[Paul Moir]

Re: Purpose and function of Carburator hose

When you tilt the engine up, there's nothing to stop fuel from pouring out of the carburetor's bowls via the main jet or carburetor vent. So that's how fuel ends up in the airbox.<br />So rather than dumping that into the water (or more importantly I suspect, the air), that hose routes the gasoline back into the manifold or crankcase (depending on the outboard) so that it can be sent through the combustion chamber and burnt.<br />The idea is that burnt gasoline is a whole lot better for the environment then volitile, unburnt gasoline. You do not gain any sort of extra power or milage from it.

 

[Stephen1]

Re: Purpose and function of Carburator hose

Paul, I accept your explaination completely. What I didn't know was that when the engine is tilted up, that would allow fuel to pour out of the carburetor from a jet or bowl or whatever it happens to be on my specific carb. I do appreciate your explaination.

 

[seahorse5]

Re: Purpose and function of Carburator hose

Stephen 1,<br /><br />The carbs should not drain gas when the motor is tilted up. If gas overflows from the carb(s), then something is wrong inside it.<br /><br />A 2-stroke outboard will "blow back" a small amount of fuelil mix as the reeds are closing and as the crankcase pressure starts to increase. That "blow back" accumulates in the air silencer box and is scavanged up by the bottom hose which has a slight vacuum on it from the intake manifold.

 

[ED21]

Re: Purpose and function of Carburator hose

I'm sure your right that gas shouldn't drain into airbox, but on mine when I run it tilted up for a while when in shallow water & then put it down , it smokes & stumbles until it digests the extra gas.<br />I assume it somehow drains from carbs, even though they don't leak normally.<br />It only takes 5 or 10 seconds until it runs OK again.<br />I've never taken off cover to observe any leak.

 

[Stephen1]

Re: Purpose and function of Carburator hose

When the motor is tilted up, when off, I do notice a small amount of fuel that drains out of the carbs. By small amount I mean probably a teaspoon or less. I will say again, I was unaware that this might be normal, but it would explain why the drain hose is there in addition to the blow back effect mentioned by "Seahorse" above. It would be helpful to know if that teaspoon is normal or if it indicates another problem. By the way the motor "seems" to operate perfectly.

 

[troska]

Re: Purpose and function of Carburator hose

I've got a '93 88hp Johnson. When tilted up, a little fuel (couple tablespoons) will drool out. I've been told here, and other places that this is normal. <br /><br />

Originally posted by Stephen1:<br /> When the motor is tilted up, when off, I do notice a small amount of fuel that drains out of the carbs. By small amount I mean probably a teaspoon or less. I will say again, I was unaware that this might be normal, but it would explain why the drain hose is there in addition to the blow back effect mentioned by "Seahorse" above. It would be helpful to know if that teaspoon is normal or if it indicates another problem. By the way the motor "seems" to operate perfectly.

 

[Stephen1]

Re: Purpose and function of Carburator hose

Well I guess if 'it's normal and it gets drawn back into the carb it's fine. This is a new/ used motor for me and I noticed the drain tube and then the fuel trickle out and just wanted to be certain that nothing deserved attention. Now if someone new where I could find another 13X19 aluminum Solas prop that Solas no longer makes I'd be even happier. it's just a great match for my rig.

 

[sangerwaker]

Re: Purpose and function of Carburator hose

Hey Stephen1, you in Anoka, MN? I grew up in Coon Rapids.

 

[Stephen1]

Re: Purpose and function of Carburator hose

Yes , that would be Anoka, Mn... is there another?? Yea I have this desease that causes me to buy used then I try to make it work and look like new or sometimes better than new. So I noticed the drain tube and a trickle of fuel and said wasupwitdat?

 

[sangerwaker]

Re: Purpose and function of Carburator hose

Better to be safe than sorry, especially when dealing with fuel. Good luck on your fix 'em up project. And no, I don't know of another Anoka, but just had to ask. I live in Fridley now, but the picture of my boat on my avatar was taken on Crooked Lake.

 

[seahorse5]

Re: Purpose and function of Carburator hose

Isn't Anoka also known as the pumpkin capital of the world ?

 

[Stephen1]

Re: Purpose and function of Carburator hose

Actually it claims to be the Halloween capital of the world but I'm not so sure that's something to be proud of, but hey if you've been here, there's not much else except 'Ol Man River' flowing by.

 

[seahorse5]

Re: Purpose and function of Carburator hose

Pumpkin? Halloween? what the hell, it was well over 30 years ago when I visited that town. <br /><br />Did do some fishing in the spillways while I was there.