I have a 1986 BBC on my airboat, all stock, except for RV cam was installed at rebuild, all cast iron except for intake changed to single plane high rise.
When i stab the gas on trailer it sturtters and pops, when it is under load in the water it is fine acclerates normal, what could be causing this?

 

carburetted?
Have you tried cleaning it out/rebuilding?

 

Finally found someone who helped me. Since power valave was deleted, and also does not hesitate under a load, they suggested changing front jets from 72 to 82, thinks it is running out of fuel.