Would the upper bolt up to an XR extension box. Does the trans have to be in the box or can it be on the engine?
Yes, it the SCT ( transmission required) uses the same over size helmut that the SCX ( shiftable) uses so that part would need to be swapped to mount either drive to the XR gimbel ring. I imagine the trans could be anywhere.
I have been pounding my SCX with a 900 hp blower motor and so far, so good.
It shifts like it has a trans. By that I mean its smooth as silk which surprised me.
I wanted to go the SCX route because I did not want the extra weight of a transmission nor the wwwwork involved in movint the engine forward ( Blower crank pulley clears bulkhead by 3/8" ) to accom a tranny in the boat. I didn't want to run an extension box on my daytona either because they seem work better with the drive on the transom.
Before buying the drive, I looked at B max and even thought about an Arneson but a single prop surface drive on a single cat would have been a handful no doubt.
I used to run a black hawk and that, although fast was twitchy at speed.
With e 400 extra hp I aded to the boat, the BH would have poofed real quick so I ended up with the SCX upper mated to a shortie SC lower.
My Daytona loved Merc upper gear sets. About every 15 to 20 hrs it ate them.
Never had lower issues so I think I am safe with the leaner lower unit. The big SCX lower may have had some high speed handling issues ( stern lift ) over 100 mph so I chose the SCX / SC hybrid version.