Speed
 

Formula 1989 272SR1 Looking for more speed and performance.
Have 330 h.p. BB with thumper exhaust with Edelbrock 750 carbs
Figuring 340 h.p. with mods
Am now running 25p Mirage tops out and was looking for any info on a better prop to run.
Hydromotive or Bravo 1?
Now running 4900 rpm WOT 68 mph with light fuel and load

Sounds like you're doing pretty well. I'd leave it like it is until it blows. To really pick up much power and speed, you will need to change blocks to at least a 454 mag.

I got the same boat with the same power and props only difference is I have Power Flow exhausts. My performance is almost identical. I think the 4 blades will hurt you top end. Three blades are generally faster since you have less drag. Four blades are good with high power where you need more bite in the water. I got a pair of 540's coming:cool:. They should wake the old girl up:eek:

OPIE272, I have the same boat with 454Mags (carbed) started with 350HP and was getting 62 GPS with Mirage 23p (not plus). I swapped the prop rotation (now rotating inward) and got 66 GPS. I added IMCO 2" shorter lowers and had to go to 4 blades, lots of trouble planing with Hydromotives 26p but topped out at 71 GPS, Bravos plane easier but slower top end. Then added added a pair of Whipples Superchargers and now running 83 GPS with a pair of labbed Bravo 30p. I think I still have a mile or two to squeeze out because my motors need refreshing (compression 10 psi down on all cylinders), a head job and better cams (one bad lobe).

The boat chinewalks quite a bit once you pass low 70's but with external steering you can handle it.

By the way the 26 Hydros belong to a friend on the board who I think will give you a good price on them if you are interested. I found my boat actually was faster with the older Mirage props than the new Mirage Plus.

speed
 

I had the outdrives replaced due to an encounter with a submerged object. I had a chance to go with the IMCO 2" shorter drives, but at the time I could not get any info on pro/con of this mod. Wasn't really wanting to take the chance of a bad combo.
Back to now..........When you reversed the rotation what props were you running and what was the handling at slow speeds, ie docking like?
Was it wirth it? Since you continued to modify the boat.

I didn't notice any deterioration in the handling by changing the direction of rotation other than the increased speeds showed the inadequacy of the original steering. I was running the Mirage 23p which by the way were not lab finished.

As far as was the direction of rotation change worth it, definitely it was free speed.

Are your props labbed and are the speeds you quote by GPS or speedo?

CayFormula
 

Sort of GPS.
I've checked my speedo with GPS before and it is about 5 MPH fast. I was running 70 by speedo and showing 66 Gps. loaded with 6 people and 130 gallons of gas
I've since ran by speedo with a light load of fuel and solo got 74 on the speedo, so I'm guessing around 68 is fair guess.
I'm running tops out with mirage 25's
Thumper exhaust and Edelbrock RPM air-gap manifolds with Edelbrock 750 electric choke carbs. fresh valve job and 2001 Bravo 1 1.50 outdrives.
With this top end I will get chine walk so I drop the trim tabs, a bump of the switch at a time, just enough to stop the roll.
I hear this is very respectable for this boat.
I just would like a little more.

OOP's
sorry. The props were reworked by a local shop. He said I would have the equivelent to lab finished props when he was done.
I just don't know if he was able to get that good of results or not. I don't know what it takes to do a "Lab Finish" Prop.
Maybe someone can run the numbers through BAM's caculator for prop slip and get some good numbers. I couldnt figure out how to put in for Twins. Or does that make a difference?

OPIE272,
Mirage Plus's are definitely slower than Mirage's. The blades are thicker and give you more drag , hurting rpms and speed. Sorry to say , OPIE , but you got the disease too. The "would like a little more" sickness. LOL

Cay,
You really gained 4 mph by swapping rotation:confused:. That's incredible:eek:. I too , have the same boat and run 25 Mirages and IMCO Power Flows. They gave me 1 to 2 mph. I top out at 67/68 for the time being:rolleyes: .

Mopower,

I literally ran 62 (got beat by a friend in Scarab) put it on the trailer, swapped the props and dropped it back in the water and got 66. I went looking for my friend again but he had already packed it up for the day (I have beaten him since though).