For some reason I can't remember if I tried the 4 blade at -1. I am pulling it apart this week and will try it. The scx lower is massive and needs to be the surface setup. Thinking of total rerig this winter with a positive box and run a surfacing prop.

Has anyone figured out why the SCX robs so much speed ?

The scx doesn't seem to take away much, however the lowers that are run with the scx 4 are just huge. There are ways to make them fast it's just lots of setup

My brother lost 20 mph with his SCXupper and -2 SCX lower compared to the SC standard

Yeah I guess that was what I was trying to say. Seems the sc lowers are much faster than the scx

Absolutely, the SCX is like dragging a 5 gallon bucket through the water compared to the SC.

Lol well said! The case is so massive really any bravo style prop is using way less blade surface. I'm totally resetting mine up and running a # 6 prop for next year.

Why did you go with the -4 drive instead of the -3 with the standard SC lower. That drive should handle 800 HP easily. Are you running a box.What prop height were you running and at what speed with the stock drive?
I was at one inch above with out the neutral box. ( 650 HP at 94 mph ) When I added the box I went up another inch.
With the -4 drive the water coming off the hull should only hit the bottom of the bullet. Is it possible that you are still too deep and causing transom lift because the bullet is acting like a ski, that and the prop being surfaced causes transom lift also. I tried a stock Maximus 5 blade prop last spring and the boat handled very badly. I had tremendus transom lift that caused the boat to ride hard on the bow. The boat was at 95 mph and still riding on both front sponsons - and the prop. Worst ride I have ever had.
It sounds to me like you need to go up another inch to inch and a half. And then run the #6 prop. That gear case needs to ride on top of the water coming off of the hull.
one other thing I did was to cut the bell off of the back of the prop - that made a noticeable lowering of the transom.

i bought the drive with the thought that I knew it would be added drag. However I thought the -4 would really be short enough to get the case out of the water. I wanted the scx lower based on I knew at some point I would be over 1000 hp.

As for now I am adding a +3 box and going to the 6 prop. Also might be adding significantly larger power. All in all the scx with the sc would have been the better choice.

The SCX does cause considerable drag due to the gear size and lower. The -4 helps if you mount the X very high. It is about 10mph slower than the XR with the same power. Above 700hp, you have only 2 choices, the SCX or Merc -8. My RPM ran 135mph with an SCX-4 and 1200 hp. Before it was supercharged and at 760hp, it ran 123mph, just took awhile to get there.

I would say to stay with the SCX and try to get your HP above 1000. The SCX doesn't make much sense below that due to the gearcase drag. If you had a 700 hp Bravo XR, it would likely run the same top speed as 900hp with SCX.