Update, Thunderbolt runs 84.4mph!
I'm fried after three long days. The K600 engines sat this one out. I was running a new 520 with modded 290 Zen cylinders. I ran a few tankfulls through with a 3116 prop. It was running around 72mph. On the third tank the prop lost a blade. The imbalance bent the shaft, cracked the strut and cracked the radio box lid. I changed the cable and went up to a 3216 prop. The boat looked crazy fast. Ran most of a tank and came it. 84.4 mph!
I then noticed the rear main brg. was moving. Probably caused by the lost blade. I changed the engine to my oldest, a 520 with Gizmo modded 28.5 zen top ends. This engine had run 83 mph in the Area 51 boat ( Violently retired ) launced the boat ran half a lap and killed the flex cable, lost a very nice prop.
I repaired the bottom end on the new engine last night, Made a trip tp Gizmo today for props and cables. I'll be back out sunday reloaded.