454 lacks power

I have a 454 utility, gas burner. That starts and runs decent but has no power. By no power I mean it can't pull itself up a hill in second gear. I've had the carb rebuilt twice, and the governor acts like it is trying to work. It smokes black slightly and pretty much needs the choke close to closed to run. Any ideas what the problem is?

Yea ya got a carb problem . There is dirt in the passages and not allowing the fuel to flow like it should . If you are the one doing the carb then pull it and set down at the bench and study it and put your glasses on and look at all the little holes get yourself a torch tip cleaner and a bucket of real carb cleaner and take it all apart and soak it for several hours , then rinse it in HOT water and start the blow drying along with running the tip cleaner thru all the little holes just don't force it and break one off in the hole then blow it out several more times . Also check and make sure that ya have a full stream of fuel coming out of the fuel line as there also maybe a blockage in the tank.

OK, first check would be basic engines 101 for a good theory of operation of spark ignition engines. Assuming that you had someone who knew what they were doing to rebuild the carb and set the float level and power and idel screws correctly, the next place I would attempt would be to re-adjust the power needle valve. A good starting point if the engine will not run is to screw the power needle valve in until it lightly bottoms out, then screw it out 1 & 1/4 to 1 & 1/2 turns. Fine adjusting can only be done correctly with the engine running. With the engine running and throttle wide open, screw the power needle in or out slowly, no more than one turn, making the fuel mixture leaner (screwed in). When the engine reaches full rpm, and warm, move the throttle lever quickly to idle, then full throttle and back to idle. If the engine is slow to respond or skips as it accelerates, screw the needle back out until the engine will accelerate without skipping. Next look at the air cleaner. Simple check would be to disconnect the breather from the carb. Black smoke is an indication that mixture is too rich for the air being taken into the engine or that the spark or compression is not adequate to fire the mixture in all cylinders properly. Check the spark by grounding out each plug with a screw driver, one at a time and listening for a change in the sound (engine skips, or just hold each wire in your hand as the engine is running). If not all plugs fire, consider replacing plugs, wires, points and condenser. Then check timing of the engine. Further would be to run a compression check. #1 Mechanic's rule is to take each step slowly, focus on what was changed since the engine ran correctly and eleminate that as a possible cause before you mess up something that does not need to be changed, ending up with several problems you don't know how to deal with.