rpm surge/fluctuation and raw gas out exhaust

bananaboatbob

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Nov 19, 2005
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mercruiser 350 ,260hp believe 82-88 engine rochester 4 barrel. new ign. coil,dist.,plugs,wires, carb rebuilt and pulled 3 times to be checked, its at least 12 years old.pulled valve cover to check top dead on #1 cylinder with timing mark and dist. all ok i have engine surge and raw gas out exhaust. i dont know anything about engines had a friend mechanic working on it.is it posibble fuel pump is bad? need new carb?
 

Don S

Honorary Moderator Emeritus
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Aug 31, 2004
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Re: rpm surge/fluctuation and raw gas out exhaust

You could have any number of problems. Ignition (point dwell, or timing), poor compression, vacuum leaks, sticking valves.<br />Could be a bad carb, dead float or sticking needle valve, or even a choke that won't open. I guess a fuel pump could be the problem. Just do a pressure test on the pump to find out.
 

Yepblaze

Lieutenant Commander
Joined
Jun 1, 2001
Messages
1,686
Re: rpm surge/fluctuation and raw gas out exhaust

How much "Raw Gas" do you have running out?<br /><br />How do you know "Raw Gas" is running out? <br /><br />What is the "Raw Gas" running out of?<br /><br />Is this while running?<br /><br />Is this while parked?<br /><br />On the water? Running or stopped?<br /><br />How does it run? Out on the water? And or at the dock?<br /><br /><br />What do you mean by surge?<br /><br />Is this something at idle in the driveway or while underway and under power?<br /><br />If it is leaking raw gas into the engine compartment stop all attemps to repair and consult a trained proffesional, as it could perhaps lead to an explosion.<br /><br /><br />If you are just running it on a hose in the driveway it might add a little "spoils" in the water coming out. Might even smell gassy. Especially while the choke might be on.
 
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