WeaponX
Charter Member
lower to mid 120's I think Greg ran 131 or so running around 80 at the start last year in his 850 boat.
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Wicked
- Thread starter Woody
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lower to mid 120's I think Greg ran 131 or so running around 80 at the start last year in his 850 boat.
glh
Charter Member
Turning a 1.35 ratio 17x39 prop with 850 horses to 149 gives it about 6% slip at 5800 rpm.
http://www.go-fast.com/Prop_Slip_Calculator.htm
That is a lot of prop for 850 horses are you guys sure no 14 year old computer wiz plugged his X-Box in the brain box of those mills?
Tantrum what speed are you getting bumping the limiter with your rig?
I am turning 36's with the same ratio and was getting about 136 with my old mills that are roughly around 850's but was not getting to my redline, props were too tall. Granted my rig is older and not carbon-fiber but my guess with the sparsness of amenities, seats, sound system, jacks for hatches and so forth... the weight cannot be to different.
Is it a 39 or a 42?
Sean H?
http://www.go-fast.com/Prop_Slip_Calculator.htm
That is a lot of prop for 850 horses are you guys sure no 14 year old computer wiz plugged his X-Box in the brain box of those mills?
Tantrum what speed are you getting bumping the limiter with your rig?
I am turning 36's with the same ratio and was getting about 136 with my old mills that are roughly around 850's but was not getting to my redline, props were too tall. Granted my rig is older and not carbon-fiber but my guess with the sparsness of amenities, seats, sound system, jacks for hatches and so forth... the weight cannot be to different.
Is it a 39 or a 42?
Sean H?
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glh
Charter Member
As a reference here is text of a 42 with 1075's tested by Tomlinson and Teague;
"Neither test driver could find a long enough stretch of water without significant crosswinds to run the 42 Race/Pleasure to its true top speed. With its 1,075-horsepower engines turning 5,850 rpm, the catamaran topped out at 146.3 mph. Both drivers believed that under better conditions the cat would top 150 mph."
It is also pushing 39"'s and the numbers check out for a 1.35 ratio with 6% slip.
"Tall 39"-pitch five-blade Hering propellers might have cost the boat a tick or two in the standing-start acceleration department, but it still managed to reach plane in 6.7 seconds."
This boat with 450hp less does 149? That is awesome bottom work.
http://www.powerboatmag.com/mti-42-race/pleasure.html
"Neither test driver could find a long enough stretch of water without significant crosswinds to run the 42 Race/Pleasure to its true top speed. With its 1,075-horsepower engines turning 5,850 rpm, the catamaran topped out at 146.3 mph. Both drivers believed that under better conditions the cat would top 150 mph."
It is also pushing 39"'s and the numbers check out for a 1.35 ratio with 6% slip.
"Tall 39"-pitch five-blade Hering propellers might have cost the boat a tick or two in the standing-start acceleration department, but it still managed to reach plane in 6.7 seconds."
This boat with 450hp less does 149? That is awesome bottom work.
http://www.powerboatmag.com/mti-42-race/pleasure.html
glh
Charter Member
Powerboat tested Hammertime / 44' also and turning 38" at 6100 rpm with 1075's they got 150 mph. mentioned to be 9500#.
http://www.powerboatmag.com/video-review-mti-44.html
http://www.powerboatmag.com/video-review-mti-44.html
Don't believe everything in Powerboat, they tend to miss a few details. My boat weights closer to 10K or just over. Computers have never seen 6100, smart craft usually kicks in about 5950 or so. Randy ran it 153 in testing, I only got 150ish with inboard rotation.
Since they are running 1in spacers in this 39, I would assume they are turning outboard. :driving:
Catagious has 1.29 gears, which is the standard set up for a 1075 MTI. Slip is going to be closer to 10% with inboard rotation. The 39 was probably a little to tall.
glh
Charter Member
Micheal even if it's a 39, 450 horses is a lot to make up it's easy enough to rebuild 850's to 1075 specs those numbers and the prop they are pushing looks more like it.
PBAM22
Charter Member
glh
Charter Member
Woody you have loads of space we have to shoehorn mine in!Finally tucked away in the garage. Tight squeeze but it fits....Now I can sleep again.
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Sean H
Charter Member
those 850's were never touched, they ran a good ecu for a poker run, but other than that they are perfectly stock. they are even the older style pulley system 850's.
but never needed outboard rotation, it is a pleasure boat.
5800/1.35/39 = 149 everyday in that boat.
the race 850's are pushing 146 at 11K pounds with a 1.35/36 restriction at 6k rpm... wicked probably only weighs around 9k +/-.
Like MC said, most of it is in the props and setup, You dont need 1000 HP to run fast in these boats. Remeber, CRC went over 160 with 750's.
bottom line, get a good set of props matched for your boat.
MarylandMark
Charter Member
I would think pleasure boats would weigh more than race boats?
Sean H
Charter Member
they added weight to the 850 minimum in hopes of slowing them down (try to keep them around 750 speeds), they later found out, the extra weight actually kept the boats off the limiter since they are restricted to a 36 prop...
most 850 race boats probably weigh around 9k-9200 with no fuel or ballast in them. Start the race at around 11k in order to finish above the 10k minimum. The boat doesn't gain any speed during the race, just acceleration as it burns fuel off.
remember, a 4 seat MTI is a race boat with the lid cut off... add a stereo and its a pleasure boat.
Woody
Charter Member
:sifone:
MarylandMark
Charter Member
Thanks Sean.
I'm sure this is a stupid question but..
If a boat is heavier, once it over comes that- would the air pack denser in the hull providing a steadier lift (for lack of a better term), which keeps the hull in the air vs say hopping a little where on the downward part of the hop more of the boat gets wetted which would slow it down?
I'll go sit in the corner now
I'm sure this is a stupid question but..
If a boat is heavier, once it over comes that- would the air pack denser in the hull providing a steadier lift (for lack of a better term), which keeps the hull in the air vs say hopping a little where on the downward part of the hop more of the boat gets wetted which would slow it down?
I'll go sit in the corner now
glh
Charter Member
Yahh but the Merc and the Audi are not in yet!ShoehornedI see all that room....could probably slide mine in next to it:bump:
glh
Charter Member
I am getting 6% with the numbers I am running with DOI on the two calculator I know. This with both set of props i have.That's 6% slip. Pretty impressive for INBOARD rotation at 149.
http://www.go-fast.com/Prop_Slip_Calculator.htm
http://www.heringpropellers.com/hering-propeller-slip.php
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