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1992 OMC 43 cobra question

D

deelan

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"when i am trying to pull a wa

"when i am trying to pull a wakeboarder out of the water, the throttle will be in drive position then as i go to a hard acceleration it dies on me about half the time. i recently had the carb adjusted to run a bit smoother, the guy was adjusting those 2 small screws on the sides of the carb..i feel like this is a adjustable problem..if anybody has any info about this please let me know...thanks in advance"
 
"I assume it's a 4 barrel.

"I assume it's a 4 barrel. If so, those little screws on the sides are air/fuel mixture idle adjustments and have no impact at higher RPM's. You could be suffering from fuel starvation caused by bad anti-siphon valve. I would try that first as its cheap ($15)and should be replaced periodaclly anyway."
 
"Hey Glenn, I was following th

"Hey Glenn, I was following this thread and have a similar problem with my 5.7 cobra with a quadrojet 4 barrel. A dumb question though where is the anti-siphon valve?"
 
The anti-syphon valve is actua

The anti-syphon valve is actually the fitting on the top of the tank where the fuel line attaches. It will have a spring loaded ball inside to prevent gas from syphoning out of the tank incase there is a fuel line break. The vacumm of the fuel pump is normally enough to overcome the spring inside but if it's gets sticky then it can cause fuel starvation.
 
"ok, thanks you guys i will tr

"ok, thanks you guys i will try that this weekend (hopefully). ill let yall know if it cures my problem"
 
"Thanks, I never new that. I h

"Thanks, I never new that. I hope thats my problem because that is simple and easy to get to. I know I have a manuel on/off valve but I never knew it had an ant-siphon valve in it."
 
"so, i went out on the lake ye

"so, i went out on the lake yesterday and it seems to be getting worse. sometimes when it died trying to fast accel. it gave me problems starting, then when it started alot of the time i would put it in drive position and it would die but, i could put it in fast idel and it was fine then i would drop it in drive..and it would die. then every now and then it would start just fine and take off just fine...im just wondering if you guys still think its the "anti-sypon valve"?"
 
"Dylan, I was having the same

"Dylan, I was having the same exact trouble with my 5.7 omc. Soon there after my engine seized up. It apparently/possibly had either a blown head gasket, cracked head, or cracked block, and had ingested water into at least one of the cylinders. I have not got the engine out and torn down yet to know for sure. It might be wise to look in that direction before you kill your engine like I did. I kept thinking it was the carb. If you get water in your cylinders it can bend a rod, which may be what has happened in my case. Mine generally ran fine when I first cranked it up, then after it got hot it had the same sypmtoms as your 4.3, and could possibly be caused by the heat after warming up causeing the crack/gap to widen. Also my 5.7 would diesel for a bit sometimes when it would die or when you would try to crank it back up, which I thought was water in the fuel but I checked that and it did not have any. You might want to save your self some $$$ and have it check out now rather than keep running it. I am now in the market for a new 5.7 engine, or to rebuild my old 5.7"
 
"Hello. I had the same proble

"Hello. I had the same problem. It ended up being the intake manifold gasket. We thought it was the carb or a fuel problem too. So my mechanic took the intake apart to replace the gasket and since he had that off, he decided to replace the head gasket and have the heads resurfaced and the guy at the machine shop said that we were lucky to have taken it in when we did, because it was on the verge of blowing. He also checked the valves and everything checked out fine. My boat is back to running great."
 
"Letti R has a point there. Th

"Letti R has a point there. That is another possibility to check out and is a lot less expensive than cracked heads, and or a block. If it is leaking it can be dumping water into you cylinders through your intake valves."
 
Try short pumps of the throttl

Try short pumps of the throttle right before you punch it. If it reacts better then the carb needs work. I rebuilt the carb on mine and the problem when away.
 
"your idle circut is to lean,

"your idle circut is to lean, it also raises your combustion chamber temps, boats need a rich idle. check your accel pump, if its ok, start richening up your idle. you dont set it like a car, so if someone set a 50rpm lean drop on it it will ruin a boat motor."
 
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