need help 1991 3.0 0mc cobra dies right after starting

bill1967hump

Cadet
Joined
Aug 8, 2010
Messages
10
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i have a 1991 sunbird 198 corsair, with a 3.0 omc cobra. i got this boat for 500.oo. it is in good shape but needed some tlc. it had 20gals of fuel in it that had sat for approx 3 yrs. when i first got boat it was turn key and ran. my buddy is a backyard mech and noted that carb was gurgling and should be rebuilt. once i got the boat home i replaced plugs,wires,cap,rotor,fuel seperator. oil was nice and clean. i ran boat a couple of times in yard on old fuel before i realized how bad that gas was. i than removed sending unit and sucked out 20gals of gas that was as red as iodine. i than took boat out for the day, it ran ok but not to its proper rpms. we ran it all day in ocean no probs. approx 2 weeks later i filled tank,launched boat then putted out approx200yards in a no wake zone when engine sputtered out and died. iwas rushed at the launch and didnt have time to let it warm up. i ended up tieing off to someone mooring to work on boat. i spent hours tring to restart motor. i would pump throttle 2-3 times, it would start then die. i did this till my batt died than got towed in.at this point i figured it must be the carb. i sent it off to be rebuilt. when i got it back i was pumped and installed hoping i would have a great season. i then attempted to start it and nothing.same problem as before. my buddy came back over and he suggested intake manifold leak, i replaced that and still same problem. so no im dead in the water. what do u think, sorry for all the info
 

bill1967hump

Cadet
Joined
Aug 8, 2010
Messages
10
Re: need help 1991 3.0 0mc cobra dies right after starting

the boat will run if i hold down choke plate covering one of the two holes on the choke plate, can run it for a while this way. but the second i take my thumb off the plate it dies. help
 

sea wolf

Lieutenant Junior Grade
Joined
Apr 3, 2002
Messages
1,219
Re: need help 1991 3.0 0mc cobra dies right after starting

Change the fuel filters, including the one on the fuel pump. Did u adjust the carb at all after u got it back from the shop? Move the throttle. Is it pumping gas into the carb?
 

tschmidty

Chief Petty Officer
Joined
Mar 24, 2010
Messages
462
Re: need help 1991 3.0 0mc cobra dies right after starting

Running while holding the choke indicates a lean condition. again, did you adjust the idle mixture screws? What is going on with fuel delivery?

You also need to look at ignition. Check the timing, change the condensor and points if you haven't lately, check the plugs and coil.
 

bill1967hump

Cadet
Joined
Aug 8, 2010
Messages
10
Re: need help 1991 3.0 0mc cobra dies right after starting

im getting spark, i took a plug and put it in the wire and held it near the block,carb has newinternal brass filter which i rechecked for blockage,can see gas just bellow inspection screw on the side of the carb. it has a new water seperator. it was timed for the old carb and did run, maybe new carb need to be retimed? i messed with those llittle fuel mix screws backin them both out up to nine half turns. appreciate you help thank you
 

bill1967hump

Cadet
Joined
Aug 8, 2010
Messages
10
Re: need help 1991 3.0 0mc cobra dies right after starting

also i disconnected fuel line from carb to check flow and it shoot across the boat..plenty of flow. gas is new,30gals. i replaced sending unit so that i could check fuel for water before putting the rebuilt carb back on. i tilted boat back and took sample from bottom back corner of tank. pumped it out with a pump and when it settled in glass jar no seperation.
 

fsjcowboy

Seaman Apprentice
Joined
Jul 22, 2009
Messages
41
Re: need help 1991 3.0 0mc cobra dies right after starting

Does this 3.0 have an elec fuel pump?
 

bill1967hump

Cadet
Joined
Aug 8, 2010
Messages
10
Re: need help 1991 3.0 0mc cobra dies right after starting

i dont believe so, it looks like it works off the engine. if i removed it i would bet that it had a arm that goes inside the block. im gonna look it up though
 

sea wolf

Lieutenant Junior Grade
Joined
Apr 3, 2002
Messages
1,219
Re: need help 1991 3.0 0mc cobra dies right after starting

It sounds like the fuel pump is fine if it's pumping the way u described. Again. Is the carb getting gas if u pump the throttle? If it's not then the float adjustment may be off. Try to prime it with a little gas & see if it starts. And keep yer mug away from the carb in case it backfires!
 
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