Carb Problem - Clueless to Problem Plz Help!

So after months of the engine running flawlessly, I go fishing and while idling through an extremely long idle zone in an area where I've always had problems for some reason, the carb started screwing up. It runs fine then about 30 seconds later gas starts spewing out of the top where that little plate with the two screws is then it dies, I can pump the bulb then turn on the choke and it'll start and run with the choke off for another 5 mins then the same thing happens, rinse repeat. I believe the top is a pathway for overflow gas to go from the float chamber, but I took it all apart cleaned every jet, passageway I could and it still does it.

I have absolutely no idea why its doing this and would greatly appreciate any help. Heres a picture with a bubble around where the gas is shooting out of.

Brand? Size? Model? Of the motor some one may have worked on one but with no motor info if is less of a chance of knowing what it could be. To me just from what you are saying your float is bad or getting stuck vacuum operated fuel pump is over powering the fuel needle/seat seal. Carb rebuild is what I would suggest for the symptoms you gave. The little rubber on the end of the fuel needle wears out and allows the bowl to flood over. Just had the same problem my self. Kit has all the parts you should need.

[url=https://www.tinboats.net/forum/viewtopic.php?p=348289#p348289 said:

crazyd » 2 minutes ago[/url]"]Brand? Size? Model? Of the motor some one may have worked on one but with no motor info if is less of a chance of knowing what it could be. To me just from what you are saying your float is bad or getting stuck vacuum operated fuel pump is over powering the fuel needle/seat seal. Carb rebuild is what I would suggest for the symptoms you gave. The little rubber on the end of the fuel needle wears out and allows the bowl to flood over. Just had the same problem my self. Kit has all the parts you should need.

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The thing is its only about a year old. I wouldn't expect a rebuild being required that fast. I'm sure its something your suggesting tho, I mean there can't be a whole lot, I just wish I could pinpoint it. Its a merc 9.9

I thought it had to be a float problem as well but upon taking it apart saw nothing wrong or out of the ordinary, everything seems to move freely and nothing seems worn. I really wanted to go fishing today, or even tomorrow, so I'm hoping someone has had a similar if not same issue because If its possible I don't want to have to wait a week to get a rebuild, I've checked before locally and couldn't find one (thought I needed one but ended up not)

I would drop the carb bowl and inspect it. Some times new doesn't have anything to do with it. Stored for a while, ethanol, manufacturer defect, etc. All can be factors. I have been working on engines for years and have bought many that didn't run or stay running and a cheap carb kit fixed most of them. It only takes a tiny bit of wear or trash to foul up a small carb.

[url=https://www.tinboats.net/forum/viewtopic.php?p=348292#p348292 said:

crazyd » 35 minutes ago[/url]"]I would drop the carb bowl and inspect it. Some times new doesn't have anything to do with it. Stored for a while, ethanol, manufacturer defect, etc. All can be factors. I have been working on engines for years and have bought many that didn't run or stay running and a cheap carb kit fixed most of them. It only takes a tiny bit of wear or trash to foul up a small carb.

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Well I did drop the bowl, cleaned all the jets and what not… But I just took it off again and can't find anything worn or looking like it could be a problem. Its as if too much gas is getting into the bowl (inspected the fuel needle as well and it looks brand new), like theres too much of a vacuum pulling too much fuel or something (just thinking out loud here) but have no idea what could cause it. I don't want to just go buy a rebuild kit without knowing what the problem is, especially if the rebuild kit could not even be the solution. Waiting a week just to realize it could've been fixed way sooner.

I agree and understand the whole sitting for a while, ethanol, manufacturer defect thing. I've delt with all three of these issue. The float had a hole in it brand new, bought a new float, sat for a while, gummed up so I cleaned carb. And I use stabilizer all the time. But this has never happened, and it just started out of nowhere.

After taking off and dismantling the carb 3 times today alone….it has to be the fuel needle not sealing….but like I said I inspected it as well as the seat and it all looks flawless, not even a spec of dirt….Could it be something else?

You may have already checked but remove the seat from the carb body and inspect the gasket, could have a slow leak that only shows up at idle.

[url=https://www.tinboats.net/forum/viewtopic.php?p=348321#p348321 said:

mphelle » 53 minutes ago[/url]"]You may have already checked but remove the seat from the carb body and inspect the gasket, could have a slow leak that only shows up at idle.

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Not sure how…theres nothing to grip onto it, Ive seen some where they are threaded in but can be taken off with a socket this is just a circle…am I supposed to take a vice grip to it and twist? Also I did a few tests, took the bowl off and checked to make sure the float, floated…in some water while attached to the carb and it works perfectly, then I put the bowl back on and manually pumped fuel into it for a solid 10 minutes and nothing ever came out. I assume that means its sealing, except when it idles….fuel everywhere.

So I'm inclined to think your right but Im not sure how to get deeper into this carb, I can't find screws, nuts, anything anywhere to get past the bowl and the top cover. Going to look at the parts fiche diagram of the carb maybe that will shed some light.

Edit: Parts fiche shows nothing….it ends at the carb body doesn't show any more detail past the basics like the bowl, gaskets around the outside and what not…

Going to try blowing into the fuel line try to get some pressure behind the gas in the bowl see what happens, Then I guess take everything off the carb that can possibly come off….don't want to but I see no other option Im completely lost its so frustrating. I've heard people suggest ultra sonic cleaning, that will probably be my last resort.

Edit 2: Well After filling up the bowl with gas, I then disconnected the line from the pump to the carb, and blew into it as hard as possible, and no gas came out of the carb, clearly it must be sealing right? What the hell is going on with this carb that only happens in idle…

I wouldn't disturb a pressed in seat, your test of applying pressure with no evidence of leakage seems to disprove my theory.

It seems like an excess of fuel in the carb would cause a stall by flooding, but your method of restarting (pump bulb plus choke) sounds more like the bowl is empty. What's the year, model/serial number?

[url=https://www.tinboats.net/forum/viewtopic.php?p=348340#p348340 said:

mphelle » 28 minutes ago[/url]"]I wouldn't disturb a pressed in seat, your test of applying pressure with no evidence of leakage seems to disprove my theory.

It seems like an excess of fuel in the carb would cause a stall by flooding, but your method of restarting (pump bulb plus choke) sounds more like the bowl is empty. What's the year, model/serial number?

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Yah thats why Im so confused and just beaten by this….. Yet every time I take the carb off the engine after doing this, its full of gas….its never empty its like it dies because of flooding, and giving it more gas helps it start……mind=blown.

Its like a 2012 merc 9.9 idk serial number.

The next test…maybe pump fuel into the carb then try to run it without the fuel line attached, I don't know what this would prove but you never know maybe its a faulty primer bulb or something. At this point Im so clueless I'll try anything.

I don't have a carb to look at, is it possible that during a cleaning that a jet passage way rubber seal was lost? Like under the metal plate on top?

[url=https://www.tinboats.net/forum/viewtopic.php?p=348343#p348343 said:

mphelle » 25 minutes ago[/url]"]I don't have a carb to look at, is it possible that during a cleaning that a jet passage way rubber seal was lost? Like under the metal plate on top?

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Doubtful, Ive been on multiple trips over the past few months since the last time the carb was off and it just happened out of the blue going through a really long idle zone, now it does it at idle all the time, when it didn't before. Heres some pics, took the top off you can see the path its coming out from that hole at the top right and comes out the bottom side….. and on the inside of the carb theres the hole at the bottom where its coming out of.

So for some reason, fuel is apparently filling up in there uncontrollably until it starts gushing out the top when idling… Im even more confused than before because I don't see why just pumping the bulb wouldn't cause the same effect…

https://i62.tinypic.com/2mrxlzt.jpg
https://i61.tinypic.com/205b4u1.jpg

Also, Idk what it does but that little plate in front of the hole with the screw in it, I've never taken it out

I'd say the little plate inside the carb is just a baffle or slosh plate. A couple of passages on top under the big plate look to be vented to atmosphere.
It's possible somewhere along the way you've lost a o-ring or gasket.
If it's running hot at slow idle it could be boiling the fuel in the carb killing the motor. If the fuel is coming from the vent this could be why.
Check your engine oil level for being overfull & if it smells like gas.

[url=https://www.tinboats.net/forum/viewtopic.php?p=348354#p348354 said:

Triple obsession » 22 minutes ago[/url]"]I'd say the little plate inside the carb is just a baffle or slosh plate. A couple of passages on top under the big plate look to be vented to atmosphere.
It's possible somewhere along the way you've lost a o-ring or gasket.
If it's running hot at slow idle it could be boiling the fuel in the carb killing the motor. If the fuel is coming from the vent this could be why.
Check your engine oil level for being overfull & if it smells like gas.

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Will do, but would it overheat in 30 seconds? This started happening a week ago, and Im just getting around to trying to fix it, so I hooked up the water to it after it sitting for a week started it and boom starts happening 20-30 seconds after idle.

Regardless, this is new info and Im stumped so I'll definitely check it out, thanks.

No it wouldn't get that hot in just 30 seconds, I was going off the long idle periods.
How does it run at different throttle settings?

I would run it at a higher rpm for a couple of minutes then idle it down. When it stalls pull the spark plugs and see it they are fuel soaked.

Do you have the big gasket under the top plate & is it in good shape, not torn etc.?
Does the float pivot free on the pin?

Just thinking out loud here.....your problem is puzzling without having the carb in hand.

[url=https://www.tinboats.net/forum/viewtopic.php?p=348363#p348363 said:

Triple obsession » 49 minutes ago[/url]"]No it wouldn't get that hot in just 30 seconds, I was going off the long idle periods.
How does it run at different throttle settings?

I would run it at a higher rpm for a couple of minutes then idle it down. When it stalls pull the spark plugs and see it they are fuel soaked.

Do you have the big gasket under the top plate & is it in good shape, not torn etc.?
Does the float pivot free on the pin?

Just thinking out loud here.....your problem is puzzling without having the carb in hand.

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At higher rpms it seems to run fine, but then again now that I remember it when I was running at higher rpm, it didn't die but would randomly have a stutter, like I'm wide open and it would quickly go back down to like half throttle on its own then back up (without me changing the throttle position)…almost like it was struggling to get fuel (which is weird since like I said the bowl is always full when I take it off or drain the bowl).


And yah the big gasket looks fine…I mean its impressed with the shape of the channels but no tears, not dried out or anything, swell as the float it pivots fine, I've tested this multiple ways and it operates just like it should.

Tell me about it man, its like a contradicting carb issue that I can't find a cause to. If any pictures would help I'd obviously be more than happy to provide anything if anyone has any clue.

…I've had issues in the past but they almost ALWAYS were caused by not running the fuel out engine after loading it up and it would sit for a few days and gum up and a simple cleaning of the jets always fixed it….but this happened after running fine for months and ran the gas out, randomly go fishing one day and it just starts happening while I'm idling.

I'll give your suggestion a try and check out the spark plugs and see how far this goes.

This is a long shot but it's worth checking. I had a similar issue years ago with a new plastic tank and a 15 I had. Check to make sure the vent on the tank is clear of obstruction. I had a fuel cap that the vent didn't work on gave me crazy flooding and starving issues.

Did you ever figure this out????