natelee

I have a 1989 31 cigerette bullet with 2002 mercury 575 sci's with xr drives. It has 3 blade 29 pitch props on it. I think I can do better. The most rpm's I've had is around 4700-4800. The motors are rated to run from 4800-5200. I'm also having a hard time with triming the drives up without the bow porpising. Any help with either problem would be greatly appreciated. Thanks !!

birdog

I ran 4 blade bravo ones on my 650hp 89 Bullet. They would
hit the limiter in cool weather. I'm suprised yours dont. The 3 blades are supposed to be faster but not handle as well.
I had the best results with my tabs level and then trim

DareDevil

i would try some 4 blade hydromotive 27's !!!!!!

4195

Does that Bullet have the notched transom? You would most likely need to have those props labbed finished to achieve your max rpm. Kreed here on the board has a 92 Bullet with twin Blower motors pushing 583 hp and he is running 28 labbed and seeing speeds in the low 80's what speed are you seeing?

natelee

Im gonna try a pair of 28p 4 blade bravos tonight and see what happens. just wondering if im gonna have enough motor to turn them. wondering if i need to do a pulley change on the blowers first to bump up the boost ?

kreed

iTrader: (2)

What boost do you have at wide open throttle?

natelee

It does not have a notched transom.

natelee

Hey kreed, these are 2002 mercury efi 575 sci's stock. I was told bye my mechanic they are 3 lbs of boost stock. what props are on your boat 3 or 4 blade ?

DareDevil

If u stay with BRAVO I props ( merc ) u need to run 26/25 4 blades since u did not get the rpm on the 29 3 blades.
for each blade u add u need to go down in pitch at least 1-2 sizes....RPM is speed !!!!!

Also , find out what your ratio is ...
kind of easy to do ...( pull 1 drive and spin the input shaft 10 times and count how often the propshaft turns ) ,,, 10 times is to be accurate...1 time is very hard to count the propshaft !!!

Should not take longer then 1 hour to do .
Hydromotives are thinner ( lighter & faster ) and more diameter ( accseleration/handling ) also they are what they are stamped, Bravo ( merc ) props are smaller then stamped.

natelee

okay guys i have some solid numbers for ya. I started with the props i bought with the boat wich are.
29p 3 blade mirage plus props.
RPM SPEED
3300 50
4000 65
4600 74

28p 4 blade brazo 1 props
RPM SPEED
3000 43
3300 49
3600 54
4000 59
4600 68.5
5100 75.9
These are gps figures
The 28's got on plane awsome and the mid range was incredible !!! I was a little dissapointed with the top end. I wanna be in the 80's any suggestions ?