RE: need help with K&B outboard carb
If it sounds like it's running lean then it probably is.
The carb that Mike showed you I don't care much for. My ex-brother-in-law had one of those and the low-speed mixture screw kept falling out and then the final straw was the carb barrel breaking in half. I prefer the older carbs on the 7.5's, the ones with the low-speed needle inside the throttle arm.
As far as a Perry carb goes, I tried one on my 7.5 OB tunnel and didn't like it.