Need help !! Props for my 31 bullet
 

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 !!

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

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

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?

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 ?

What boost do you have at wide open throttle?

It does not have a notched transom.

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 ?

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.

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 ?

27 hydromotive and run it to 5400 RPM its ok ,,,,just not for hours and hours at that RPM !!

Well, if you are truely at only 3 LBS of boost at WOT(3 blades) at 4600, then what boost do you have at 5100(4 blades)? Need to know how much boost your making at WOT on both sets of props. Is there a boost gauge? Also, if you just bought this boat, check the timing at total advance to see where its set, very important. Im not sure where it should be on a 575 EFI, but lots of people on the board here will set you straight, dont want to burn any pistons!!! I run Labbed 28 Bravo 1 4 blades. Have done 81.2 MPH at 5300 RPM. They are a great "all around" prop. They say the 3 blade is faster at WOT, but IMO, the 4 blade is right there too. I would love to try your 3 blades on my boat if you decide to sell them. If you have them labbed, you may get 3 to 400 more RPM out of them. Talk to Brett at BBlades about the lab finishing, not Brad... you need to speak with Brett. But first get you boost #'s straight. If your at 3 LBS, a smaller pully may get you to where you want to be !!! :drink:

Thats interesting, I thought all 89s had the notch. Must have been an early 89

I would have Brett lab the 28s and live with it. Like you said..The mid-range is great.I ran mine at Erie alot and top speed was not everything in rough water

Birdog....you had a fast Bullet. What have you got for Top Gun speeds????

Listen to Birdog this is good advice. Labbing the 28's will give you more rpm which you need and you should gain 3 maybe 4 miles an hour. My guess is this boat with the motors in stock form should run high 70' maybe in perfect conditions 80. You have to remember the air quality this time of year sucks and it def. will result in a loss of hp. labb finish 4's it will get on plane faster better cruise and mid range, and handle better. The notch transom is probably good for a 1-2 mph.

Judging by his MPH and RPM #s, he will be alot faster with the 3 blades if he can get the RPMs up to 5000. Like maybe 80+ MPH with the 3 blades just lab finishing them! So, I say lab both sets and use the 3 blades for race days, and the 4 blades for family days....best of both worlds.

I truly dont no the boost i dont have boost gauges on the boat. I didnt think boost would change with different props. If the stock boost is 3 pounds shouldnt it be 3 pounds at the max rpm of the motor ?

I talked to tom at hydromotive. He recommended 27p 5 blade props for the best wot rpm with the most efficient cruising rpm. He also thought there 4 blade 28p would work good to. He thought i could pull a few more rpms with theres and a few more mph. Do you guys think i should try a set of them or just get my 29p labbed ?

I would try the labbing the 28 but i dont own them :). I borrowed them from a naughbor to try them. Read my newest post i put and let me know what u think. thanks

Well I have had great luck with the Bravo 1 props I bought from BBlabes. Talk to Brett the owner of BBlades and he can pretty much tell you how fast he can make your boat go...right over the phone! Hes the man when it comes to props. Ive new used Hydros, so I cant advise you on them. You need to know what RPM your engines make peak power at. 5200 sounds about right. Boost will increase with RPM. So for example, with the 3 blades at 4600, you may only be making 2 lbs of boost at WOT. With the 4 blades at 5100, you may be making 3 lbs of boost. But to set the boat up properly, you need to know how much boost your actually making and at what RPM the engines make peak power. 3 LBS of boost is conservative and you could be robbing yourself of some speed!....

Boost pressure on the gauge really does not change based on rpm. Boost pressure changes based on the load placed on the engine. If you rev an SC'd engine in neutral to 5000 rpm, it will hardly show any boost. If you put a heavy load on it, it will make boost pressure. If you are at WOT, the engine should make the about same boost pressure whether its at 4600 or 5100rpms. Boost pressure is not the amount the air/fuel being moved though. At more rpm, the blower is spinning faster and moving more air/fuel mix.

The 575SCI makes 4# of boost stock. Recommended WOT range is 4800-5200rpms. Run it at 5100-5300 to make the most HP and get the best top speed. Running it at 4600rpms WOT is harder on it than running it at 5300rpms WOT.

I would not go with 5 blade props. You don't need them and they are harder on drives. I highly doubt you would be able spin 27 Hydros to even 4800rpms.
I would get a set of Bravo 1 28's and have them custom labbed by BBlades. They will be a good all around prop with a very good top end #.
The 29 Mirages are too big. You may want to try some 27's. That should get the rpms to around 5000 and probably a mph or 2 faster than the 29's.

Griff, i did not say anything about 5 blade props...but 4 blade hydros are thinner and lighter then the merc and he ran 28 4 blade mercs, so why would a 4 blade 27 hydro not work ??:party-smiley-004:

The Bullet was a rocket..In cool air it would bang the limiters everytime I pushed it. It needed more prop but..Running Erie i liked the Mid range

I built the motors In the TG for blowers..Low comp, big blower cams. But never put them on. I just havent had the time to fool with it. It runs about 75 and only running it once or twice a year...Thats fine...:drink: Unless I find a Screaming deal on a pair of 10-71s or 871s

I still say send a pair of 28s to Brett and tell him what you want it to do...He has done props for many of Bullets...

Well guys I ended up trying the 27p 5 blades by hydramotive and they were awsome. Gets on plane sweet good mid range and the best of all I seen 80 mph at 5200 rpm. These props are awsome. I was able to trim the boat up the furthest with these props. The 5 blade props have so much more control over the boat than the 3 or 4 blades it is awsome !! Now I'm just stuck on weather I should do the boost and ign. Upgrade by AZ SPEED ? It sounds like a really sweet setup they have. Taking the blowers to 6 bls of boost, msd ignition, upgrade the computers, rev limiter from 5300 to 5600. I really don't want to mess with my reliability. What should I do ?

I feel stupid !..Somehow i thought you had 3 blade 27s.. not 5 blade...I would have loved to try those on my Bullet !
Be careful though...I bet they will destroy Bravos If you are not careful

The only way i would jump to 6lbs of boost is with an Intercooler

Well after getting a set of 27 5 blade from hydramotive and a set of 28 4 blade bravos from bblades. I ordered a set of 4 blade hydramotive 28's of offshore only. They turned out being the best and at a 1/4 of the price !!! 81 mph @ 5200 I love it. A few more dollars come on 85 !!!

Congrats on 80+ MPH !!!:drink:

Just .02 here ..... Do some background on AS ....no personal experience here ....just what I have read ....check it out ....looks like your definitely headed in the right direction ...good luck ....m