I run a Formula 292 singel engine a F1 boat.
I run it with a big block 557 with a whipple supercharger 1130hp around 1250nw, i have out driver IMCO SCX 1.34 with the 1400 SCX under, top speed 110mph at 6250rpm, i have more rpm up to 6600rpm its dyno to.

I run Bravo 1 32" lab, it has work out best so far, but this session i have broke 2 props, that one blade is broken, i know to much power for this props, and why i ask for your help.

The hull is with two step and the weighs is about 4851lbs

what would you recommend

The only way you are not going throw blades off with that much hp is to go to SSM6 props.

IMCO does make a #6 prop shaft for the SCX 1400 lower.

I believe someone makes an adapter..........

SCX's can be ordered with 3 different prop shafts.
#6 Speed Master Prop Shaft & Bearing Carrier Kit SCX,SCX 4, SCT, SCXT

The SCX 1400 can be bought from IMCO with SSM6 propshaft. Not sure why you would have prop clearance issues. There is no -2 on the SCX 1400.