Gas spraying out plug holes during compression test. Normal?

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May 8, 2022
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I replaced the carburetor on my Mercruiser 5.7L 350 engine solely because the throttle linkage was getting still and it stuck a few times. It ran fine, just a bit sticky. In hindsight that was a pretty trivial thing to complain about. So I purchased this new, re-built, beautiful Rochester Quadrajet. Everything matched up and it was an easy install even for me. Started it up and the engine has never ran worse. I have a couple other posts here trying to find help figuring out what could be wrong. I got help from several of you and check if ports were misaligned, I had the right base gasket, air leaks etc. but nothing I did made a difference. Results I got from a compression test convinced me the motor was shot and before I started prepping for removal this afternoon, I found a loose valve stem in the compression tester's quick connect. I fixed that and got a completely different set of numbers from a new test but during this test with the coil wire disconnected and all plugs pulled, fuel poured out of the plug holes while I cranked the motor. I kept it in neutral the whole time and never touched the throttle. Both sides of the block was soaked in gas. I'm obviously not a mechanic but I still feel stupid asking if this is normal. If not, what is going on? Is there anything I can do? Sorry for writing a book. I really tried to keep it short.
 
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Sounds like the float needle/seat is stuck allowing fuel to overflow. If you "tap" on the front of the carb it might unstick itself. Hold a medium screw driver by the tip tapping the carb with the handle.
 

ZeeOSix

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Gas "pouring out" of the spark plug holes is not normal. Make sure the choke isn't closed on the carb. If it's not, sounds like the carb is still pourng lots of fuel into the intake manifold. Fuel level way too high perhaps?
 
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Gas "pouring out" of the spark plug holes is not normal. Make sure the choke isn't closed on the carb. If it's not, sounds like the carb is still pourng lots of fuel into the intake manifold. Fuel level way too high perhaps?
Choke on or off has nothing to do with the amount of fuel being dumped into the cylinders. Choke regulates air into cylinders..

Agree with post # 2.
 
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If you have not done anything to disable the fuel system then you would still have fuel being drawn into the cylinders however you would see this as a fine mist at worst popping up from the spark plug holes with all the spark plugs out while cranking. Fuel should not be poring out of anywhere. I Would return the new carb for a exchange or refund. You didn’t have these issues with your old carb.
 
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If your boat ran fine before the carb swap and bad after, it's your carb. For no reason ever, should fuel be pouring out of the plug holes! Choke, no choke, fuel system connected or not. Carbs don't work like that! Stop attempting to test compression immediately before we hear about you and your fireball on "Boating news of the week"
 
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ZeeOSix

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Choke on or off has nothing to do with the amount of fuel being dumped into the cylinders. Choke regulates air into cylinders..

Agree with post # 2.
If the choke is fully closed, it creates more vacuum on the manifold side of the carb and can cause it to draw more fuel through the carb jets. Especially if the choke is fully closed and the throttle butterflies are held wide open.
 
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