cprperformance

I was just wondering if anyone has done any extensive testing on a notched 36 for X- dimension/ drive height. I have a 36 with XR's and sportmasters. the center of the nose on my drive is 5/8 above the running surface. Last year the boat ran 120mph at 52-5300rpm with stock 36 B1's and 1.26 ratio in the drives. Running 2X700's. Had a little prop slip getting on plane and prop slip is a little on the high side (16%) so I sent props to BBlades to get labbed.
Got the props back and definitely appear to have more cup in them. Boat now planes much easier but MPH or RPM on top has not changed. Any Ideas?
I know that on earlier cat boats that I have owned just by putting shorties on picked up 10-12mph by freeing the boat up. Was wondering if that might be the case here. Any help would be greatly appreciated!

obrien

If I remember correctly we have run some of the boats up to 1.5" up from the bottom. The biggest factor will be water pressure. are you sure you are running 1.26 ratio? Most of these boats had 1.35 drives You can play with the toe on the drives. Another good idea would be to have the lower units blue printed. you will likely find more speed there. If you can find a set of herrings to test, that would be a good idea as well. Are the labbed props now at a true 36" pitch? Stock bravo props always measure a bit smaller than what they are stamped

cprperformance

Yes, definitely have 1.26 ratio. I would assume that Brett made them a true 36 pitch when he labbed them. It runs a solid 122mph now but still bumps the limiters. I really think that I need to try a set of Herings. I emailed them but haven't heard back. I tried it the other day with a set of 2" instead of my 2 1/2 spacers above the lowers but couldn't get a good feel for it because water was too rough. That should make it about 1 1/4 above the bottom. I'll keep posted my results when I get a good test in. Did seem to loose some water pressure, but like I said water was rough.

Cobra100+

iTrader: (3)

I cant remember the height from centerline, but the top of the transom assy touches the rubrail on my 36. All the others i've seen have a 2" gap between the two.

SPECTRECAT

I have a full bottom 36 with 12" standard boxes. I'm running SCX4 drives with 2" spacers. My X is 3 1/4" up right now. I am running #6 props 17 1/4 x 36 - 18 rake. Boat runs good but too much hop. I had Bravo's with sport master lowers (standard length) before and the boat had zero hop. Still trying to dial it in. Power is 800 HP

obrien

is your boat the one that was originally rigged with ilmore engines for sonny banister?

SPECTRECAT

No
This boat had MDG 650 when it was new. Always had the boxes and full bottom since new.

Donzi Dude

that would be my boat

obrien

cool I was wondering where that boat ended up. How is it running?

Donzi Dude

running great , ilmors with scx drives = super dependable package.
was thinking about selling it but it would be hard to replace.
for the record the x is 3 inches from the bottom
from watching it running with a go pro I think 2 1/2" would be about right for my boat.