Before I go and spend $2K on a new prop, I just want to explore the engine vibe on throttle back some more. On my Skyranger 80hp rotax it is still vibrating when closing the throttle. A nice still clear day today some did some experimenting again. Wondering if this could be a carb issue still. Carbs sync checked and still perfect with the carbmate, engine idles excellent at 1600rpm. Engine goes well at low level except for some vibe when closing throttle which kicks in at 4400rpm, clears by 3800rpm but re-opening throttle it vibes until after about 4400rpm again at which point it runs fine. Climbing to altitude of 3500ft, vibe kicks in at different rpm range, more like 4700rpm but again will not clear itself, need to fully close throttle and re-open. Even after this at altitude, engine harsher in the range of 4600-4800rpm which is right where I need it! If I open throttle and keep straight and level, runs smooth but vibe kicks in again at approx 4800rpm. It is definitely worse at altitude then low level (e.g. 500-1000ft) which makes me wonder about a carb issue/altitude compensating mechanism. I don't profess to know how the compensator works but willing to find out. If the vibe was a prop issue, would it occur in a different rpm range with different altitude? If I had some air induction leak still present, I would imagine the idle would be rough and the carb sync off again. It makes no difference if aux fuel pump on or not, engine has 124 hrs on it now from new, installed July last year, Prop is 2 blade fixed pitch wood that gives WOT climb of 5500 and not quite 5800 straight/level. Have done all the other stuff like checked spark plug gaps, checked torque settings on engine mount bolts. Engine mount rubbers are in fine shape and are the same age as the motor. I don't run a return fuel line and don't monitor fuel pressure but there are no indications the engine is running rich and runs great at full throttle and idle (e.g. during descent). Again, any thoughts from you all appreciated. Will go now and watch video on pulling the carbs apart....
