Idle speed & mix adjustment - black smoke when just started.

[rodrigwa2005]

This is for a 3.0 LX, 1997 mercruiser - GM, I/O engine.<br /><br />I did the pre-adjustment per the service manual on these two settings...tried the engine, out of the water...other than running on idle slightly above the recommended idle speed ( aprox 100 rpm's above , it ran very smoothly, so much I got gladly surprised as this is the first time I did myself...no hesitation, no noticeable smoke, just running fine.<br /><br />I left it as that to complete the final adjustments with the boat on open water as recommended...that's when I noticed that when the engine is just started and prior to get warm ( I'd say below 130 F) black smoke was leaving the exhaust - not much, but certainly much more that when I did the pre-adj.<br /><br />Looking for suggestions on what to look for.<br /><br />Thanks!

 

[Don S]

Re: Idle speed & mix adjustment - black smoke when just started.

That black smoke is because it's running rich because the choke is on. As the engine warms and the choke opens up it doesn't run as rich.<br />It's quite normal for carbed engines.

 

[rodrigwa2005]

Re: Idle speed & mix adjustment - black smoke when just started.

Thanks Don!

 

[ron7000]

Re: Idle speed & mix adjustment - black smoke when just started.

I have a 2002 3L. I've adjusted the choke so that it's almost open all the time. Mine needs little choke to start except when its 50F or colder. You can adjust yours real easy by loosing 3 screws on the choke cover then rotating the plastic cover where the two wires connect to. You see the choke flap either open all the way with no spring action trying to close it or it'll close with heavy spring action keeping it closed. Just adjust it to where its not as closed under heavy spring when cold and see if that helps. If not then go some more, if it don't start when cold as easy then you went too far.