Mercruiser 4.3 wont stay running

[Wellcraft170]

Hey guys. I’ve got 1990 2 bbl 4.3 Mercruiser.. will not stay running. Couple weeks ago i had it out and it wouldn't start when hot.. had to wait a few hours before i could go again and on the way in i couldnt get off plane and smelled gas. Had a friend rebuild the carb but he didnt start it up so i just tried running it on the hose before heading to the lake and it wont stay running. Just sounds bad and even after giving it some throttle it dies.... any thoughts here? Is it maybe the fuel pump? Heres a video example with some weird noise at the end too..

 

[Wellcraft170]

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[Wellcraft170]

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[Wellcraft170]

Also want to add that when it is running, it sounds like a hissing noise can be heard pretty clearly.. dont know if that has anything to do with it

 

[harringtondav]

Basic root cause analysis: Ask what changed before the problem. Did your boat have this problem before the carb rebuild? What issue caused you to rebuild the carb?

Your answers will help narrow down the suspects. With what you've stated...hissing noises can be intake manifold leaks. Result can be lean mixture. Possibly from a bad carb reinstallation to the manifold. ...bad/missing gasket, loose fasteners, loose or missing choke pull off hose.

Gas odor could be from a loose fuel inlet connection, missing air horn gasket or loose fasteners connecting the air horn to the carb body, or incorrect float height or float needle installation.

So back to the questions. If things were better before the rebuild, I guess the rebuild or carb installation was botched.

 

[Wellcraft170]

Basic root cause analysis: Ask what changed before the problem. Did your boat have this problem before the carb rebuild? What issue caused you to rebuild the carb?

Your answers will help narrow down the suspects. With what you've stated...hissing noises can be intake manifold leaks. Result can be lean mixture. Possibly from a bad carb reinstallation to the manifold. ...bad/missing gasket, loose fasteners, loose or missing choke pull off hose.

Gas odor could be from a loose fuel inlet connection, missing air horn gasket or loose fasteners connecting the air horn to the carb body, or incorrect float height or float needle installation.

So back to the questions. If things were better before the rebuild, I guess the rebuild or carb installation was botched.

Before the rebuild: boat starts fine cold, wouldn’t start hot. Had to wait a few hours for it to be “cold” again for it to start. On the way back in, it wouldn’t plane out.. smelled gas.

after the rebuild: hard to start, would stall after about 15 seconds. Wouldnt start hot just like before. This was on the hose too.

reason for carb rebuild? The guy who did it is a personal friend of my uncles, not just some random mechanic but i guess he assumed the carb needed to be rebuilt from all the original symptoms i told him about

 

[Wellcraft170]

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