idles ok when it warms up, but when I stick it in gear it drops from 800rpm to 400 and dies, how do I adjust the air screws to keep it from stalling under load.

1. make sure your power valves are not opening when the vacuum drops going into gear.

2. try a slightly richer mixture at idle.

3. Add some timing at idle.

Get a can of carb. cleaner and clean out the air bleeds. Use the little red straw to force the cleaner through them. Then make sure the front & rear throttle plates are open the same amount. Then adjust your idle mixture the same amount screwing them out makes it richer.

These are fresh rebuilt, on fresh engines, when you put it in gear the rpms drop so far it dies, im wondering about how to get the idle air screws adjusted right.

theres really no magical setting on the idle mix screws, you just kinda give the engine what it wants. How far out from seated are the screws now? 800RPM in neutral might be a little low for a modified setup. You may wanna try 900-1000RPM warmed up in neutral.

What do you have for ignition setup? With a healthy cammed dominator carb'd engine, sometimes its very hard to get them to idle worth a crap if you have the typical mercruiser 10* base timing setting.

Sounds like it's lean at idle. Where are the idle mixture screws set at now? Turn them counter clockwise to richen it up.

Did you change anything in the engine? cam, compression.

put a timing light on it..see if advance is falling off causing it to stall...can seem like a carb issue...

I will say this i was leary of these engines as most of you have seen me ask several questions but it was at 85mph and climbing still when it got a little loose feeling and the trim was not working correctly, and my indicators are screwed way up, but she ran better than i thought.

not a carb issue, its all about timing johnny. slam it into gear and jab the throttle forward fast enough it wont die.. problem solved and youre welcome