ORIGINAL: Drmeff
originally it was a front intake engine with the carb just as you described. That didnt fit very well in my boat, and I had another K&B 3.5 with the exact same crank case but with a rear rotor carb. Well I took the front assembly off the front carb engine and switched it with the rear carb engine's front assembly. I then took out the front carb engines back plate and replaced that with the rear rotor carb. I can tell the carb is spinning and it is sucking in air when it is turned over. Like I was saying, when I cover the carb it sucks in fuel and runs until that fuel is used up. It just doesn't seem to be able to pull in the fuel by itself. I had this problem with the front carb and now the rear carb too. The rear carb seems a bit better but still no go! All the fuel line is new, just for an FYI
The crank case is a little different between the crank induction (early) inboard, and the later drum rotor inboard... For the drum rotor, the case is cut away in the area of the rotor, allowing flow up to the boost ports. While it probably wouldn't perform as it should with the early case not being machined for the drum rotor, it should still run... I also suspect that you may have something plugged up at the needle or tank pickup, or maybe your pressure fitting in the pipe could be plugged...(?) I'd also check to see that you don't have any pressure/vacuum leaks around the carb or case gaskets...