25 Daytona SCX4
 

Has anyone had any success with the -4 on the Daytona running the surface drive #6 props? I have been testing about every Bravo setup under the sun and cant get the MPH back.
We installed the #6 shaft and not sure where to start prop wise, setup is 800 hp a 1" above.

did you try the IMCO SCX -3 upper with the standard shortie lower?
I have a 26 with 800+ HP running a MERC X drive upper and an IMCO -3 lower at 2 inches above and an IMCO neutral extension box.
I am playing with props right now.
I plan on buying the SCX -3 upper this winter. ( If not sooner )

Just noticed you are in my backyard. DO you go to Hardy?

We go 1 or 2 times a year, usually go to Torch or Traverse Bay.

I pulled of the XR and a -2 shorty and started new with the SCX4. I have been trying all the drive heights with bravo props and its not getting the speed. I am waiting for some #6 prop to try. Like everyone knows the scx is just a massive gear case. So we are hoping to keep the drive high and run some large diam. wheels. I will prob have the lower blue printed this winter and maybe a power upgrade. Hoping someone has tried the similar setup to help avoid a massive prop bill! lol

Have you tried a lab finished Maximus, it worked well for a buddy on a 26 Daytona with SCX-4, at about 3/4 inch above bottom

Mine is 2 inches above the bottom and it doesn't like a 5 blade prop. I am running a 28 4 blade Bravo prop. IF your prop shaft is high enough the only thing in the water is the scag and the prop. The bottom of the bullet should be touching the water also.
I am playing with props right now. Best I have seen is 112 at 6100 RPM with a 1:34 ratio drive.
I have a stock 28 pitch Maximus 5 blade prop. The best speed I could get was 95 with the boat heavy on the bow. It caused WAY too much transom lift.
I was at HOT BOAT weekend today with more than 1/2 tanks of fuel I got 108 every time I hit it.

What power? Are you running the full SCX upper and Lower? Or the SC lower? I am going to try the no spacers again which puts me 1" up from bottom and try the bravos. I tried so many setups I'm loosing my mind!

I have tried the P-5 and the P- 5x both handle great but speed is way down

I don't think your prop shaft is high enough for the -4 drive. That is a surface drive. You need to go up another inch to fully surface that drive.
Right now I am running a MERC. X drive upper modified to swing a Maximus prop with an IMCO standard -3 lower. That put me at 7/8 inch above the botttom.
Last year I redid everything on the inside and outside of the transom. I raised the X another 1 1/8 inch for a total of 2 inches above and added an IMCO neutral extension box. I shortened the trim rams 3/4 inch and with some cutting and grinding was able to get a lot more negative trim so that I can get on plane with the BRAVO 4 blade prop. My slip #'s are in the 4% range. I was going to buy the -3 SCX upper and mate it with my -3 lower. The upper is the weak link with the MERC. drive. Can you get on plane with a 4 blade???

I am running 800+ HP naturally aspirated 598 cubic inch that I built last summer.

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.

What prop did you run on the scx4 1200hp setup?