I have a 86 38ft Cigarette with twin 454's. Yesterday I installed a thunderbolt iginiton, cap, rotor, and holley 800's that a buddy had taken off of his boat in perfect working order.

Here is the problem I am having. It sounds like its missing at low rpms and idle. When you go from about 1100 rpms it will hold there and shoot up to about 2000 rpms. If you take it out and run it if you ease into it it will never get on plane it pops and back fires, but if you throttle up fast it will get past that and runs fine in the 3000 to 4000 range. Both motors are acting the exact same.

We have it set at 10 degrees timing right now but we have tried a few diffrent spots. We have checked all the wires and verified the firing order a few times.

Any ideas would be very very much appreciated as I have spent 2 days trying diffrent things.

Just a silly question... make sure the choke is not engaged. When it pops and bangs, is there smoke?

I posted on MWBP as well. I think your issue is carb related and more than likely you fouled out the spark plugs.

yeah the choke is wipe open. I get a puff of smoke on the larger backfires.

Ok well if you get a pop upon easing into the throttle, but it works smoothly if you just hammer it wide open, then my suggestion is to try one of two things.... 1. Change the pump cam for the squirter or 2. maybe even try a smaller squirter.

Definitely check the plugs and make sure they are not fouled... if in doubt change them out. You problem is definitely carb related. An ignition problem would not clear up once the engine is under a hard load.

The smoke tells me it is way too fat at part throttle, but once you open it up the airflow meets the fuel requirements. You might also clean every one of the air bleeds in the carb.

Ok thanks I will try that this weekend

You may have a vacuum leak. Did you try to use the old carb to intake manifold gasket? How about a vacuum hose off somewhere? Water in the fuel?

If I suspect a vacuum leak, an easy check is to spray carb cleaner around the carburetor base while idling. If the RPM changes, that's most likely the cause.