4bus

Curious if someone has experience with shorty drives on a 38 side by side hull, twin step (big steps, last generation)





Trying to squeeze some more performance out of my boat this winter, without adding more HP. Current set up is stock 575sci's with standard XR's. Factory X is 18" x 34". Has broke 90 mph a few times but real every day numbers are 88-89 at 5150 RPM, spinning B1 4 blade 32 pitch. I am rebuilding the blowers this winter, adding teflon strips (slight boost gain at same rpm) and having the ecu reprogrammed for drivability improvements.

I have a friend that has 2 -2 imco lowers. Would have loved to try them but they need a little work so I would have to buy as is, fix, then try them :/ Curious if anyone else has used them and seen performance gains on a similar set up.

Looking to be in low to mid 90 mph everyday with just set up changes (drive, prop, bottom?). Let me know if it is even possible

Thanks

mcprodesign

I was running about 90 ( 89.990 Gps). then I did the shorties and got my proshafts centers about 5/8 to1 3/16 below the surface. Right away I went 94.8.( with some small chop) I am going to try other props here when the air gets cooler. I would say do it, if you can swith to a surface prop. Like Hering or Maximus. When I had stock drives I ran hydro props. Right now it is a little slower planing but still planes of nicely w 7 or 8 people full of fuel etc. I just put it at about 3000 and let it plane . It will plane faster a 4,000 rpms. I have the smaller steps on a blueprinted bottom. Mine had spacers on the drives so I went up 3 inches total. My headers are 5/8 from the gunnel in the rear so they are as High as possible wiitout major change. I think you will get 3,4 mph w the change.

p's I think your XR internals will fit right in the -2 cases , they did on my sportmasters.
Pic at speed

prostockcat

1 5/8 is where the prop shaft is from the bottom of the boat?

mcprodesign

From what I have gathered. 1-2 inches below the bottom is best for the drive ( xr) 1-2 above the bottom is more speed and harder to plane, plus tough on the drive..

Chad