89 268 w/single 454 Merc Carb help please

[Wardy549]

Ok, so in the beginning my boat would fire right up idle great and at around 2000 rpm it would fall sputter choke etc. I took the carb apart and it was clogged up and rusty spring and ball within. I bought a rebuild kit and installed. Then I could not get it to fire. So thinking I messed it up, I bought a new rebuilt quadrajet for a 454. Marine. Only difference was the new carb has an electronic choke vs the old one that links to the block. So, I put the new carb on and the boat fires up but at 500 rpm it spits and coughs like lean pop.
adjusting the two low/high screws at the base of the carb it literally has no reaction turned totally in or turned all out.
continues to run the same.
jetting issue? Or??
If anyone has my same set up I would love to know exactly what carb I should use if this one is wrong.
i do have a edelbrock I think that's correct" intake manifold other then that the engine is factory.
thank you much!
wardy

 

[tgreene]

If you have the same 454 that I do and I think you do idle spec is 650-700 rpm in gear. Could it just be your idle adjustment?

 

[hottoddie]

There are many things that can cause your symptoms. Did you install a new base gasket along with new carb? It can be install uoside down and will cause a vacuum leak along with your symptoms. A bad distributor cap or plug wires can cause similar symptoms. Worse case bad or sticking intake or exhaust valves can also cause these symptoms. How old is the motor? Is it raw or fresh water cooled? How many hours are on it? If you have an Eldelbrock carb it may have come off a car engine and would be illegal to install on a boat engine.

 

[dvx216]

If the carb was all clogged up sounds like you need to check the rest of the fuel system. Plus at this point you need to know what your fuel pressure is by installing a pressure gauge in the fuel line before the carb. Auto Zone has a rental tool to do this. If you found rusty springs then there's was water at some time in your fuel. Change you fuel separator then cut it open to see what's inside. Inspected your fuel tank. Fuel pressure should be around 4-8 psi. Nine times out of ten if it falls on its face off an idle its starving for fuel.