Stepped vs Non-Stepped Formula 271
11-15-2018 | 11:02 PM
#25
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Joined: Nov 2008
Posts: 595
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I have had both an SR1 271 with a 454 Mag and a 271 Fastech with a 502. The sr1 did around 60 @ 5000. The Fastech did low 60's (62-63) @ 5000. All speeds on Garmin GPS.
11-19-2018 | 03:22 AM
#26
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Joined: Apr 2007
Posts: 533
Likes: 3
From: Oslo
So except if you compare the result from Jwurl 68 mph, I should be kind of happy with my 63,6 gps mph on the SR1 hull non stepped.
I am looking forward to test the boat next season, changed from an old Bravo1 XR Drive to a Bravo1 X Drive, I have been tod the te XR drive steal more power
then the other x drive :-) Do not now if it will be any better result, lets see. I am also considering to change to Custome Marine headers (CMI Top Split Headers)
The advertising says that they gains power and speed ;-)
I am looking forward to test the boat next season, changed from an old Bravo1 XR Drive to a Bravo1 X Drive, I have been tod the te XR drive steal more power
then the other x drive :-) Do not now if it will be any better result, lets see. I am also considering to change to Custome Marine headers (CMI Top Split Headers)
The advertising says that they gains power and speed ;-)
11-19-2018 | 07:51 PM
#27
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Joined: Aug 2007
Posts: 676
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From: Greensboro,NC
Yes the XR drives suck power and speed. My original drive was a 1.65 ratio standard Bravo. Boat was running 68 mph on GPS. I blew the drive and installed a brand new 1.50 Ratio XR. Prop was then switch from a 28p to a 24p Bravo 1 4 blade. Speed was now down to 63 -64 on GPS at best. I have put roughly $50K plus in a complete repower since. 715hp EFI 540 CI, 280 tabs, Imco full hydraulic steering, ect. Now when the boat tops 78 mph it has pretty major chine walk and gets scary. Best I have seen is low 80s wthout having to back out of the throttle. Still have plenty of throttle and RPM left so I think the boat could do mid 80s set up right. Now I am debating having the hull blue printed, possibly messing with extension boxes and drive heights, or just move up to a larger boat with twins. jeff Wurl
11-20-2018 | 04:13 AM
#28
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Joined: Apr 2007
Posts: 533
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From: Oslo
Dear Jwurl Very interresting to read your results.. some questions
1 Did you do any testing of propellers before you ending up with the labbed Bravo1 28 pich, what was the results/ improvment
2 What about the ratio 1.65 to1.50 do you think that this will be a big difference when and if you find the correct propeller ? Or is
it only the difference between XR and X drive that has such an impact on the result… My new drive is an Xdrive 1.50
3 How did you mount your 280 tabs ? Mine is parallel mounted take a look at the picture in my earlier post. The owner before me
had a 540 kompressor engine with 840 HP, said that it was a big help regarding the chinewalk ;-)
I am considering to buy a used Procharger to my 496 HO on the lowest boost 3,5 psi it will give my engine aprox 550 hp
that should maybe get me in the low 70 ties :-)
1 Did you do any testing of propellers before you ending up with the labbed Bravo1 28 pich, what was the results/ improvment
2 What about the ratio 1.65 to1.50 do you think that this will be a big difference when and if you find the correct propeller ? Or is
it only the difference between XR and X drive that has such an impact on the result… My new drive is an Xdrive 1.50
3 How did you mount your 280 tabs ? Mine is parallel mounted take a look at the picture in my earlier post. The owner before me
had a 540 kompressor engine with 840 HP, said that it was a big help regarding the chinewalk ;-)
I am considering to buy a used Procharger to my 496 HO on the lowest boost 3,5 psi it will give my engine aprox 550 hp
that should maybe get me in the low 70 ties :-)
11-20-2018 | 05:04 AM
#29
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Joined: Apr 2007
Posts: 533
Likes: 3
From: Oslo
This is what the owner before me posted at this Forum :-)
Well I have a 1993 271 sr1.
I have installed a 540 whipple engine. 830 Hp
I run a bravo xr 1.50 and are into testing propellers,
I run now 80 miles, at 5500 rpm, with a bravo1 28 pitch.
The problem is now that the boat bounces from side to side and get really uncomfortable to drive.
So I am wondering what to do..
Second post
This winter, the boat is taken apart, the transom was pretty rotten so most of the plywood in the transom was removed, now the transom is like new again. I am going to lift the x dimensions up 3" for the transom, montage 280 k planes and lantham double ram steering. So I hope the boat will not do the chine walk. The boat has also going thru a diet.
I think I can lighten the boat for aprox 250 pounds or more. Time will show how much I can remove without sacrifising the comfort of the boat.
( The boat was not lighten only rebuild, and the X dimensions where only lifted aprox 1.5 ") I am pretty sure he got 84 mph out of it, but never found the
perfect propeller ;-)
According to Kjetil the the owner before me, the 280 K Planes helped a lot against the Chinewalk. Becuase of the mounting of them he had to mount the Hydraulic steering in away that it was impossible to manouver the boat in slow speed and at the docks, so I removed it. I bought the boat with out the engine as well.
Well I have a 1993 271 sr1.
I have installed a 540 whipple engine. 830 Hp
I run a bravo xr 1.50 and are into testing propellers,
I run now 80 miles, at 5500 rpm, with a bravo1 28 pitch.
The problem is now that the boat bounces from side to side and get really uncomfortable to drive.
So I am wondering what to do..
Second post
This winter, the boat is taken apart, the transom was pretty rotten so most of the plywood in the transom was removed, now the transom is like new again. I am going to lift the x dimensions up 3" for the transom, montage 280 k planes and lantham double ram steering. So I hope the boat will not do the chine walk. The boat has also going thru a diet.
I think I can lighten the boat for aprox 250 pounds or more. Time will show how much I can remove without sacrifising the comfort of the boat.
( The boat was not lighten only rebuild, and the X dimensions where only lifted aprox 1.5 ") I am pretty sure he got 84 mph out of it, but never found the
perfect propeller ;-)
According to Kjetil the the owner before me, the 280 K Planes helped a lot against the Chinewalk. Becuase of the mounting of them he had to mount the Hydraulic steering in away that it was impossible to manouver the boat in slow speed and at the docks, so I removed it. I bought the boat with out the engine as well.
11-20-2018 | 08:25 PM
#30
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Joined: Nov 2008
Posts: 595
Likes: 31
Dear Jwurl Very interresting to read your results.. some questions
1 Did you do any testing of propellers before you ending up with the labbed Bravo1 28 pich, what was the results/ improvment
2 What about the ratio 1.65 to1.50 do you think that this will be a big difference when and if you find the correct propeller ? Or is
it only the difference between XR and X drive that has such an impact on the result… My new drive is an Xdrive 1.50
1 Did you do any testing of propellers before you ending up with the labbed Bravo1 28 pich, what was the results/ improvment
2 What about the ratio 1.65 to1.50 do you think that this will be a big difference when and if you find the correct propeller ? Or is
it only the difference between XR and X drive that has such an impact on the result… My new drive is an Xdrive 1.50
On mine we tested 26/28/30. Top speed on 26/28 were the same, just 26 @ 6K, and 28 @ 5500. The 30 would only pull 5K, and was slower. But it cruised at super low RPM.
XR straight cut gears eat HP, but also less likely to break if pushing HP through it. Mine was a standard B1 drive and it was run WOT all the time, but it was not beat on getting on plane or jumping.
