Originally Posted by thatsmrmastercraft
The relationship between mixture screws and idle speed screw needs to be proper. If the mixture screws are in too far, you can make the carb idle on the main metering circuit - though not very nicely. As Cloaked said, start with the idle mixture screws 1 1/2 turns out and get you idle speed set properly.
If the diaphragm on your power valve (and it should be 2.5) is ruptured, it will run full rich and give you black smoke coming out the exhaust. The only true way to test it is to remove it and hold the outer diameter of it while trying to gently twist the pointy end. If it turns freely it is bad. By turning your mixture screws in all the way, the engine can still run if there is a significant base gasket leak.
Thanks. It's running good now and the mixture screws are responding. I don't honestly know what exactly fixed it but I'm not going to argue with success!
For those of you that have done rebuilds on this carb where did you set the float levels? Level seems way too high but I may have had some needle and seat issues too. I did find a generic guide in the link below but I would think the marine application would be a little different given the angle the engine sits at in the boat?