I have read on another forum that a single 400R 22 Talon has had several shafts break under acceleration from idle and props were lost. Merc replaced all parts and supposedly changed how the prop shafts were being manufactured.

saw with my own eyes a nor tech cc brake 2 off on the same outing.

Our buddies 21 Liberator 300R broke a prop shaft Jan 2. Merc warranted the shaft & Merc prop. He doesn't fly this boat, he is just learning it.

the only reason 400R's are breaking prop shafts is if they are being surfaced. The 390 Nor-Tech that broke 2 shafts was a quad 400 boat being run very hard AND was both outside shafts (happened when was aggressively turning causing outside props to cavitate).

Ive been told the nor tech 390 with quad 400's is definitely faster, but not as agile or reliable as trip 400's....yet another reason I probably will not go with a quad set up.
a trip 450 or 500 set up would be phenomenal but, I don't think mercury will release them just yet. We shall see...