sucking in air when throttle pushed down fast!

[waterdawg69]

i have a 160hp mercrusier 4.1 liter had carb rebuilt last week. new spark plugs, filter, plug wires, ect. when i put the throttle down it sounds like it sucking in alot of air and dies sometimes if i don't pull it back. how can i fix this!! thanks for any help. ohh it has a roch 2bll 2 jet carb

 

[thunderroad]

Re: sucking in air when throttle pushed down fast!

My first guess would be a problem with the accelerator pump inside the carb. It squirts a little fuel into the throat at first acceleration. Check to see that there are two solid streams shooting into the throat when you open the throttle. There's a little check ball under the spring in the accelerator pump that makes it shoot the fuel into the throat instead of back into the bowl. This little item (smaller than a BB) is often lost or overlooked when a carb is dissambled. DId you replace the points and if so, did you reset the engine timing afterwards? Slow timing could cause it to be doggy at acceleration also.

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

had the boat timmed when i put points in set at 6 degrees and sometimes its like a poping sound in the carb when you give it gas. like poping popcorn. when it idling is the gas suposed to like dribble down of a stream?

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

it even did this before the carb was rebuilt

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

boat pic

 

[cheburashka]

Re: sucking in air when throttle pushed down fast!

It shouldn't be dribbling gas visibly when at idle. Usually that's a sign that the float valve in the carb is leaking. I'd advise pulling the carb and having it gone through again. Did a shop do the work on the carb?

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

yes, should it be a fast spray like using a spray bottle bottle

 

[thunderroad]

Re: sucking in air when throttle pushed down fast!

I can't look at your pictures because I'm on dial-up and thanks to the new board we'll all have our boats put away for the summer before the pics come up on my screen.
It may take another carb kit and rebuild to get you going. Something is amiss in there. You shouldn't see a stream of gas "dribbling" in there at idle. Maybe the float is too high, or maybe the gasket under the venturi cluster isn't sealing up good. Whatever it is...you're gonna have to take another look at the carb. I'm no carb expert. I had a guy in our shop rebuild mine this spring and he did a great job. Runs great. It's a 2bbl Rochester also and he remarked that it was a simple carburetor.
...easy for him to say.....

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

what abut the two screws at the bottom of the carb. you think they might not be set right. just noticed you boat is a 69. mine is a the boat is a 65 lake flight and the motor is a 67. paid $450 for the only thing that was wrong at the timewas the guy could only get it to fire for a sec. and he gave up. but the only thing it was.
Was the fuel pick up in the gas tank was clogged with gas. it a really nice boat . all the gauges work . so it was his lost my gain.

 

[cheburashka]

Re: sucking in air when throttle pushed down fast!

Your pictures aren't loading at all.

You need to be more specific about what's happening with the gas. If the engine is just idling, there should be no gas visible in the carb throat. When you pump the accelerator hard, there should be a spray of gas. The Rochesters are simple, but there's still a lot that can go wrong. I'm rebuilding last week's rebuild as we speak.

The screws at the bottom control idle speed. I doubt that there's anything you can do with them that would cause the kind of problem you're describing. I don't think there's any way around pulling that carb and checking the float.

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

sorry about the pics don't know whats wrong, but there is one thing that the shop said they did not replace was a long spring wih a small bb like thing in it or something they said it was fine, but if its he float should it be raised more. or lowered thanks for the help

 

[thunderroad]

Re: sucking in air when throttle pushed down fast!

I put a kit in my carburetor last summer. When I started it up it ran ok but I could see gas blubbering out around the venturi cluster and down the throat. I took it back apart and found that I had left a tiny piece of the old gasket under the venturi cluster. This kept the new gasket from sealing it up. I scraped it clean and re-installed and it worked ok...but was doggy at acceleration. I had a mechanic rebuild it again this spring and he found that I had left out the little check ball under the accelerator pump. Like I said, it runs great now. If the BB thing at the end of the spring that the guy is talking about is the power valve, I didn't replace mine either time because a new one didn't come in the kit and the old one seemed to be ok.
I still think you've got another carb rebuild in your future. Look on the bright side....carb kits are relatively cheap.
good luck

 

[searay3]

Re: sucking in air when throttle pushed down fast!

Not quite understanding a lot of what you are saying, but that just may be a language issue. As far as the tank, if the pickup tube was clogged, chances are there is crap in the tank. Has to be cleaned to even start running right. Next would be the anti-siphon, does it now have crap in it or is partially stuck. Change all fuel filters including the one that goes in right at the carb/fuel line. Now for the carb....if you are lookng down the throat and you open the throttle, there has to be fuel squirting in two solid streams. There should be no dribble in there while idleing. You say it's a 1967....I don't think I would trust a shop that rebuilds a carb and doesn't change the accel pump on a carb that could be 40+ years old:} Your best bet would be to service the tank and fuel lines and replace the carb, not rebuild since it could be so old. IMO

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

the fuel line have been cleanned. filter spark plus,ect. but i also have the filter in the fuel pump plus a in line filter before the carb it rum great a wot smooth. but im gonna take it out later to let you all know how it does. thanks for the help.dd

 

[waterdawg69]

Re: sucking in air when throttle pushed down fast!

and the gas tank was removed and cleaned really good.