I have a Mustang 50 that until today had been run about 1/2 hour, this engine is supposedly a Fuji 50. Now, according to towers info the Fuji 50 should turn a 20x8 prop at between 8,100 and 8,400 rpm, today all I could get with a Zinger 20x8 running on Amoco 93 octane, oil at 25 to 1, recommended for break in, is 7,350. Will it pick up some more rpm as it gets more run time on it, or is that it. I have a Fuji 50 so called muffler on it, it is a big empty can with a 1 inch outlet pipe.