Best prop for a 1993 Formula 271
 

I have a single 502 efi motor in the boat and took it out for its first ride last sunday. Noticed it would only get up to about 55mph and it seemed like it was underpitched. What kind of prop would you use for this boat? The tach read 5000 rpms with the hammer down and the drive trimmed up. Im thinking about a 24 pitch 4 plade or possibly a 25 pitch?? let me know the best prop to use. Im not majorly concerned with getting out of the hole id rather have the top end speed. Would like to see it do a little better than 60mph.

Thanks for your help.

what prop are you running now?

I believe its a 23 mirage. 3 blade

I don't think there is any way your going to spin a 25-26 pitch 4 blade prop at the proper rpms. Your boat is very similar to the formula 242. with 415 hp the 242 will do about 61-63. Your boat is 1 foot longer, 3" wider and close to 1000 lbs heavier. 58 would be my guess as to a realistic top speed as it is. Your going to need to modify your engine if you want more speed. To me your prop seems correct. That engine is supposed to be propped around 48-5100 rpms which is right where you are.

it is what it is ......mo power ...

What prop and pitch are you running on your 242 415hp to get 63mph?

I'm not. I'm building a 550 hp bbc and I'm hoping to see 70 mph. From the research I've done on this it seems the 330 is good for about 53, the 365 does about 57 and the 502 boats from what I've read are in the 61-63 range. The HP 500 motor = 69. My 242 SS did 47 with a 350 mag (270 hp). The twin engine boats did about 66 but an extra engine and drive is a lot of extra weight and drag. I'm selling my SS and redoing an LS I picked up over the winter.

I have a Bravo 1 22". I run 59 mph.

I need to GPS mine but I thought I was running around 53mph at 6K feet with a 22 Bravo 1 at 4,800rpm I've got a 365 with a 177 weiand at 4lbs boost at 6K feet.

Im thinking of borrowing my friends 24 pitch 4 blade. Theres no reason why my boat couldnt spin that prop. He has a 2004 30ft checkmate convincor with a single 496 mag and consitently hits speeds of 65mph with that prop. So im thinking thats gotta be the right setup for me... any advice?

There is almost no way that prop is going to work on your boat. When you go from a 3 to a 4 blade prop you need to decrease your pitch because you're lowing your prop slip. Going from a 23 Mirage to a 24 bravo your going to loose about 3-400 rpms which will put you at about 4600 and thats too low for your engine. Plus your going to loose speed anyway going from a Mirage to a Bravo. You can try it, but I doubt your going to get the results your looking for. My suggestion is to get a 25 pitch Mirage and have BBlades lab it. That might get you close to 60.

I have a bud here in S.OH who has the same boat and motor.. Bravo 1 1.50 He runs 61mph and bounces of the rev limiter.. Stock 502mag efi.. He's running a 22p
He also removed the silent thunder off the back and picked up 200rpm more..

hmmm... i hear you on the 25 pitch mirage, i know that 3 blades are usually the faster prop to go with. I guess im just going to have to play the guessing game. Ill try the 24 bravo cause i have that prop readily available, and ill have to talk to a few shops around here and see if theyll let me test a 25 mirage or a 22 4 blade.. Im not trying to go a whole lot faster, i just want to see consistent speeds of 60mph. Thanks for the continued advise. Does anyone know anyone in the southeast michigan area that will let you test props? Also, labbing was an option, however i boat in a very shallow lake and frequently tie up in shallow sandbars, so im not sure if labbing it will be the best option because i heard labbing makes props weaker. Is there any truth to this?

Ive got the same boat with a 21 mirage on it boat goes 55 thats it, tried a 22 hydro and had better holeshot and cruise mph less, Silent the efi runs a tad better then the carb motors

Give Michigan Wheel in Grand Rapids a call. I think they have a demo program. I'm not sure if they only do their props only or if they also do Mercury. Either way it may be a good place to start. BBlades in wisconsin has a great demo program, I would certainly call them.

Please let us know what you had found w/ the 24p and the others that you tried. I have a 1993 271 that had a 800+ blower motor in it that run in the 80's w/ a 28p four blade and over this winter I decided to build a 454 with a stroker kit to turn it in to a 496 and it will be on the dyno shorty rough guess is 600-640hp and I'm going to need another prop. I'm thinking spliting the deference and going w/ a 26p

After some research and looking at the same boats as mine that are for sale online, it looks like they are running either a 24pitch bravo 1 4 blade, or a 25 pitch mirage. I will see if i can get ahold of any of these to test and see what the outcome is.

I also noticed the newer 271 fastecks with the same motor as mine are running 26 pitch 4 blades stock from the formula factory. But that seems to big for my boat and it may be because the newer formulas have the stepped hulls?? I will call BBlades today and see what they think about this whole thing. And again, all advice is appreciated.

Thanks

if you notice also on the newer 271's its a left hand prop

Thanks for pointing that out i was curious about that.. Does a left hand prop get more mph? whats the advantage of them?

be lying if I said I knew, maybe someone here does??? i do know that you can't put a left hand on now and run it you will hurt the drive

some of the Fastech's have/had 1.65 drives .....m

Bravo drives can run in either direction with no problems. A fastech 271 runs a left hand prop. I have tested a right hand prop on my fastech and it lists to one side pretty bad. That is why they run a left hand prop. With a 1.50 drive I found a 22p Bravo one 4 blade works best. Around 61 mph with a full tank of fuel and 4 passengers. I now have a 700hp 540 in my Fastech. Currently running 80 GPS with a lot of tuning to go. Jeff Wurl

93 271 SR1 stock
 

I think I have the 1.5 gear ratio. Not sure. 4800 rpm gets me 52 mph on the GPS. stock 502 MPI with 22p 4 Bravo 1 blade. Not too many places in NJ where the water is flat enough to open it up. This boat does cruise nice about in 2-3 footers off shore @ 3200 30 mph. I wonder if I would have better economy with a higher pitch?

400 hours on the motor and I want to keep it in one piece as long as possible.

You should definetly get 55 outta that boat, might wanna try a 21 mirage

Well since other people are trying to dial in a prop for their boat too ill post my findings.

Original prop on my boat when i bought it 23 mirage (test run was with 2 people and 1/4 tank of gas.)
5000 rpms at wot
57mph (not gps speed)
Tons of prop slip

Just tried a 4 blade 24 pitch yesterday on my boat with 3/4 tank of gas and 4 passengers.
4700 rpms at wot (not enough rpms for my motor)
54mph (gps Speed, The speedo guage read 57 still so really no change in speed)
No prop slip that i could tell. (motor actually felt bogged down)

Contemplating what i should do next. I think im going to try a 25 mirage plus 3 blade and get it labbed to make the rpms that i need. I think this is the prop that i need. I just think that this thing should go a little faster than that. Im going to look into a rebuild on the motor over the winter but for now i want to just play with some props.

Oh yeah, the boat is a 271 formula with a 502 mag.

Update:

I just went out today by myself with 1/2 tank of gas and got it to 58.1 mph gps. Kinda windy and chopy though so i didnt let it sit at wot for too long. With the 24 pitch 4 blade

What were your RPMs?

26 p bravo prop will get me to 62 on the gps. once and a while with a tailwind and 2 foot chop i can see 65. that is alone and 1/4 tank of fuel.

You could lab the 24" B1 that would probably get you 4,900rpm. I would Lab a 22" B1 and spin it 5200rpm low fuel, driver and no load. That should put you right around 5K witha normal load.

Well I have just the same boat a 1993 271 sr-1

My boat had a 502 carb, and it blow up when the oil cooler made a huge leak and trowed the oil into the sea.

Well it was in the middel of summer and had no time to fix the engine at that time, (I live in Norway and the summer is short)

So I bougt a new 496 Ho an installed with bravo 1 with 1.50

I called to formula and asked them what prop to use they said a 23 mirage II will be the best.

I got that with the dealer I bougt hte engine from.

At first the boat ran 56 mph, and then I removed the bottom paint it had. then I got 59 mph

Then I bougt cmi headers and it picked up some more, speed.
now my top is 63 mph.

I have then 4900 rpm at wot.
But the boat is very sensitive for weigth in the bow, if the water tank is full it will not go more than 55 mph at wot.

I have the silent thunder to but it wil be removed now together with taht heavy sun pad and those heavy chairs.

I will make a a new sun pad in divinicell and buy new chairs that are much lighter. Maby I will get a couple of more mph from that.

I did test a bavo 1 24" but then i got just 4600 rpm and 57 mph, So I think this boat is best with mirage props.

Kjetil Johansen
Arendal Norway.

I'll be going out today with a 26 bravo one, warmed over 496, 560hp post some #'s later.

still around 52 4800 on the gps with my 93-sr 271 502 MPI bravo 1 22" LH. I believe it's a 1.5 my serial starts with 0F04. Found a place to open it up. Delaware River. Still running on last year's gas almost full tank one passenger and full water tank. funny I always thought it was a 23 prop. looks like I have a couple very small dings, size of a pencil point. Is that enough to throw it off? It will take a full weekend to run out about 90 gallons.

What did you end up with on this run?

64mph with 7 people and about 80 gallons of fuel. 3 of the people were kids " 75pounds and under" we were on Vacation with it so we did not go for any high speed runs I feel I should be a round 67-70 with myself and one other. I have two more props to try Bravo one 28p four blade and a 27p three blade. I keep you updated. Oh, ya I had a Hyd lifter bad that was cracked and was not pumping up so I was down some Hp and I Dried up the Exhaust.

93 Sr-1 502 Mpi B1 22"
 

Still @ 4800 and 52 mph. Still have 1/2 tank last year's (treated) gas. I am almost certain fresh gas will get me to 5000 rpm. I guess I will be happy with that for now. running great!

:drink:Dude ......its July!!!!! ....burn that Fuel ...........:drink:

Hmm
I do 50 mph with my bottom painted 1988 Formula 242 SS
Bravo1 454 33o Hp

I am sure you should go much faster with 2 people omboard
in your 271 with 502 , should be 60+

nope, I twist a mirage 21, 49-5000 r's and 58.7 on the best day so far

My engine is complitely rebuild this year and I think very fresh, but I did not know there where so mouch difference
in speed betwin 242 and 271.

I know that with a brand new 496 not HO but normal 375 HP
The 242 LS does 57,5 mph

88242LS have you tried a mirage 23+ yet??

my old 242ls ran 59 with a stock 454/365hp 21 mirage plus havent tried the 23 yet my boat struggles outta the whole as it is