OMC 4.3 liter Cobra issue

[OfficialJaii]

So, I bought a 91 Galaxy boat with a 4.3 OMC Cobra engine. I took it out to the lake to test it out and it ran fine and strong at full throttle for the first 10 minutes, then it died. It turned out to be a bad alternator. Anyways, I replaced that, and while I was working on it I rebuilt the carb Holley 4 barrel. I took it out to the lake again and at idle it would sometimes die. When I would finally get it going at a very slow speed it was fine, but when I would drop the throttle anywhere past 1/4 of the way it would stall or die. Anyone have a similar issue or know what's wrong?

 

[Speak]

Sounds like you a running out of fuel, by this I mean the float bowl in the carb is not holding enough fuel to support the fuel demand. This can be adjusted in the carb by allowing the needle and seat to stay open longer raising the fuel level in the bowl Also might want to make sure your fuel pump is delivering enough fuel to said carb. Sounds like the engine is slurping up the gas faster than it can be resupplied. Check the accelerator pump in the carb as well. Just my opinion.

 

[bruceb58]

Describe how you set the carb's idle jets after you did your rebuild.

Is your fuel new or is old fuel that was in the tank when you purchased the boat.

What is the condition of all your ignition components. Have you changed them since you purchased the boat?

BTW, your boat engine isn't going to die after running for 10 minutes because an alternator died unless the battery was already severely discharged.

Low float levels usually cause you to have a problem when you apply throttle and use more fuel...not when you are running at idle.

 

[OfficialJaii]

I will definitely look into this, I will adjust these and see what it does.

Sounds like you a running out of fuel, by this I mean the float bowl in the carb is not holding enough fuel to support the fuel demand. This can be adjusted in the carb by allowing the needle and seat to stay open longer raising the fuel level in the bowl Also might want to make sure your fuel pump is delivering enough fuel to said carb. Sounds like the engine is slurping up the gas faster than it can be resupplied. Check the accelerator pump in the carb as well. Just my opinion.

 

[OfficialJaii]

Its 8 month+ fuel in the boat. Didn't change if just added an entire thing of seafoam. Also, elaborate on the ignition parts?

Describe how you set the carb's idle jets after you did your rebuild.

Is your fuel new or is old fuel that was in the tank when you purchased the boat.

What is the condition of all your ignition components. Have you changed them since you purchased the boat?

BTW, your boat engine isn't going to die after running for 10 minutes because an alternator died unless the battery was already severely discharged.

Low float levels usually cause you to have a problem when you apply throttle and use more fuel...not when you are running at idle.

 

[bruceb58]

spark plugs, spark plug wires, cap...rotor!

Describe how you set the idle mixture screws.

 

[OfficialJaii]

I closed them all the way up, then opened them 1 1/2 turns! Is there any way to check the adequate amount of mixture? Thanks in advance.

spark plugs, spark plug wires, cap...rotor!

Describe how you set the idle mixture screws.

 

[bruceb58]

Do a google search. You will find many procedures. You can do it with a vacuum gauge or just turn them for max idle speed an back off when the idle speed finally falls.
http://www.stangtv.com/news/how-to-properly-adjust-the-idle-mixture-on-holley-carburetors/

 

[lasko1]

I just had similar issue when throttling up, it'd fall flat on its face prior to the boat planing out....did not have the stalling issue at idle though. Mine was fixed by a sort of "shotgun approach" which I'm not fond of because I don't know the "exact" cause.
Anyway, I changed: 1- the small fuel filter at carb, 2- the fuel/water separator, 3- points and condenser. Boat runs great now. I do still have a studder at 3/4 throttle when the 4barrel is kicking in but it runs great at WOT. Hope this helps.