extension box for formula 271???
10-21-2009, 09:51 PM
#1
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extension box for formula 271???
Was looking for anybody's past experience on something similar to mine.
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
10-22-2009, 02:24 PM
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Was looking for anybody's past experience on something similar to mine.
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
Holly crap this thing gotta fly, how fast? hows it handle?
10-22-2009, 05:01 PM
#3
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You should ask on the race forum, but I believe the prop shaft at2" below the bottom is where many of the straight bottom single engine vee race boats are set up. Consider getting all the hook out of the bottom. It will not cost much to repair the bottom and you are at speeds this could make a significant difference. You can control the mid-range porpoise you will likely get with the drive and tab settings.
10-22-2009, 06:58 PM
#4
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Was looking for anybody's past experience on something similar to mine.
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
I have a 271 formula sr-1 non stepped v bottom with a 825 hp n/a bbc and max machine modified XR running a 28 pitch bravo 1 non labbed. It currently runs 83 at 5500rpm.
I have already raised the x dimension 2" up from stock for a total of about 5 1/5 " from propshaft centerline to running surface. It is equipped with 24" eddie marine k planes and imco hydraulic steering. We have taken as much of the "hook" out of the hull without getting into the fiberglass but some of a hook still remains.
My question is, I'm thinking of adding a 3" raise imco extension box. Will it work? Will it add the speed I would think it would. Anyone with some similar experience's advice would be greatly appreciated.
Thanks
10-23-2009, 12:06 AM
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Thanks, I'll look into it. If I remember right, when the blackhawk drive was introduced in the late 90's, the boat builders that got the most out of that setup actually had a little hook. By raising the propshaft so high, it kinda acts like a surface drive. I don't understand how a hook could help, but I'm not a boat builder either!
88242, it is unbelievable how well this thing handles the power and speed. It doesn't even chine walk when you have it set up right. I like that I can cruise in the mid 70's and it feels real good. It is a little hairy on the big end, you have to be on top of things.
Sam
88242, it is unbelievable how well this thing handles the power and speed. It doesn't even chine walk when you have it set up right. I like that I can cruise in the mid 70's and it feels real good. It is a little hairy on the big end, you have to be on top of things.
Sam
10-23-2009, 04:51 AM
#6
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Sam,
be careful taking all the hook out. I did that on my 251 Checkmate and ran into problems in rough water. There was a thread from years ago that we discussed what happen. Long story.. see if you can find it.
Dick
be careful taking all the hook out. I did that on my 251 Checkmate and ran into problems in rough water. There was a thread from years ago that we discussed what happen. Long story.. see if you can find it.
Dick
10-23-2009, 05:26 PM
#8
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