1989 2.3 OMC Carb Backfire, runs sometimes, dies shortly after

Shootemdownace

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I put a tune up kit in, replaced the plugs, drained the gas, new fuel/water seperater and rebuilt the carb. It ran fine before all this then wouldn't start the next day. Followed the timing setting guide. When it finally starts it runs great for about thirty seconds then dies. Sometimes it floods while trying to start and sometimes it doesn't get enough gas. It will spin over freely almost like no compression, flooded is my guess, then I keep cranking then the motor seems to build compression and either will start or backfire like crazy. Few minutes later bam.....she runs but only for 30 seconds and then dies. The float was set to spec on the carb rebuild but I have messed around in both directions a little bit to see if it makes a difference and it seems to have little to no effect. I'm am baffled. I really need some help. Trying to get out on the water tomorrow!!!!
 

Bondo

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It will spin over freely almost like no compression, flooded is my guess, then I keep cranking then the motor seems to build compression

Ayuh,..... Welcome Aboard,...... Maybe a compression test is in order,.....

Sounds like the carb is really screwed up,....
How's the rest of the fuel system,..??
Is the fuel pump, pumpin',..??
 

Shootemdownace

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Compression is over 130 on all four. POS carb? It's completely rebuilt to spec now. Redid the float to spec few minutes ago. Same thing.
 

Shootemdownace

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Update....since I feel like I'm alone here, maybe this will help someone else. Bought a timing light and timed it. It will not start at all. Backfires through the carb. Reset the float to what the rebuild cab kit said for as close to my engine as possible. It floods the engine so apparently that is incorrect. It keeps dumping fuel into the carb when I'm done cranking....too much fuel. The carb is completely clean on the inside. It is a Rochester 2gc. I think I'm missing two little bushings that surround the inlet tubes that feed the Venturi however it ran fine without those before. When it backfires it only does it on one cylinder like the other cylinders are not even trying to fire. I have spark and I have 12v at the coil on both sides with the key on. I did not change any of that before so I'm not sure what it should be. I get 12v when ground to each side but not across the coil. When I measure across the coil (both posts) it reads 0. Still not running. Good compression, good spark, timing is on.... It's got to be that darn carb! I bought new NGK plugs that I will try later tonight.
 

Bondo

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Ayuh,.... You obviously have a carb problem, so fix that 1st,....
 

Shootemdownace

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Jul 22, 2016
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Ayuh,.... You obviously have a carb problem, so fix that 1st,....

That's the goal. Just not sure what's left other than just buying a new carb AND figuring out which one replaces the 2gc. I'm not sure without accurate float information I will be able to fix this one!
 

Shootemdownace

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At a complete loss. Changed the carb out to a known good running carb. After some time cranking it will seem like it gains compression and then fire up for a few seconds and then die. It spins freely up to that point and you can hear the engine kind of bog down as if it is building compression and then it starts, runs for a few seconds and dies. Completely at a loss. Any help would be great.
 
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