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Drive ratio

Old 01-12-2017, 04:41 PM
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Originally Posted by GPM
The design of the SCX lower housing is the problem area, there's a huge lump in the middle that only got worse when they made the 1400. The only reason to buy an SCX is for durability, running the SCX upper with an SC lower doesn't really make a lot of sense if you're already breaking SC lowers.
I'll have no idea 'till I get it together and see what breaks..


So, if NOT an SCX what would you run
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Old 01-12-2017, 05:55 PM
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Originally Posted by Boatally Insane
I'll have no idea 'till I get it together and see what breaks..


So, if NOT an SCX what would you run
That's what sucks, the options are very limited, my brother spent the 18 grand for the complete SCX, ran it last season without breaking but it took 20 mph off the top end. It could just be the wrong boat for the application, 26 cat.
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Old 01-12-2017, 09:20 PM
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[QUOTE=GPM;4519067]
Originally Posted by Keith Atlanta
What about the new SCX blueprinted lower? Looks like its more efficient than an XR by a mile.[/QUOTE

If you're talking about the 1400, look at it up close and then tell us what you think. The bullet is about an inch bigger than the SC so it doesn't match up to a Bravo prop, there's a massive lump in the middle of the housing and on and on.
It looks like they blended it. In most step bottom or pad boats wont the lump be insignificant?

Surely on your DCB thats not even in the water is it?
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Old 01-12-2017, 09:43 PM
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[QUOTE=Keith Atlanta;4519163]
Originally Posted by GPM

It looks like they blended it. In most step bottom or pad boats wont the lump be insignificant?

Surely on your DCB thats not even in the water is it?
I can't post pictures or videos,but yes the massive lump does affect it, I'm talking about the -2 not the -4, look at one in person if possible. You be the judge.
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Old 01-15-2017, 01:52 PM
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Originally Posted by Boatally Insane
Trying to decide what outdrive gear ratio to go with after my upcoming engine swap...

The boat is a Velocity 290sc.. Currently has a 496 Mag HO and a 1.5 ratio Bravo X ..

Running a Hydromotive P5X 25p, fastest I've seen has been 69.9 MPH..

Others with the same hull / power have reported 72 mph with a labbed Bravo 28....

My new engine dyno'd at 1020 HP @6000 RPM in full marine dress..

So, using a boat speed calculator using 72 mph at 425 horse puts me at 110 mph with 1020 hp..
(which seems close as I know of another 290sc with 750 ish hp that runs 94 mph ...)


SO, that being said, figuring on about 11% slip, a 33 pitch (Bravo 34 ?) prop would theoretically put my boat at 110 mph at 6000 RPM with a 1.5 ratio drive..
OR 29 pitch (Bravo 30 ?) with a 1.30 gear ratio..


Which one would you go with ?

I've come across a few used Bmax drives & Imco SCx's with the 1.3 ratio..
haven't come across any used with the 1.5 ratio yet, but may be able to swing a new one once I get my other boat sold..

THANKS !

Doug
Before I hijacked your thread, not knowing the weight of your boat, I would think the 1.5 ratio would pull out better than a 1.30. I don't know if I would rely on any of those calculators, maybe start with a 30 or 32 prop.
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Old 01-15-2017, 03:52 PM
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With a cat I also wouldn't think that the size of the bullet would make that much difference. Run the drive higher and spin a prop with more diameter.
On my boat the bottom of the bullet is touching the water. The bullet is not going through the water. I even had to lower the water intake slot for better water pressure. On a single engine 29 ft boat I don't think that you would be able to get on plane with the prop that high. Even with a notched transom.
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Old 01-15-2017, 05:31 PM
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Originally Posted by Tinkerer
With a cat I also wouldn't think that the size of the bullet would make that much difference. Run the drive higher and spin a prop with more diameter.
On my boat the bottom of the bullet is touching the water. The bullet is not going through the water. I even had to lower the water intake slot for better water pressure. On a single engine 29 ft boat I don't think that you would be able to get on plane with the prop that high. Even with a notched transom.
Just curious, what drive heigth was Steve Tripp running on his 26 cat
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Old 01-15-2017, 05:52 PM
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Originally Posted by GPM
Before I hijacked your thread, not knowing the weight of your boat, I would think the 1.5 ratio would pull out better than a 1.30. I don't know if I would rely on any of those calculators, maybe start with a 30 or 32 prop.
I would think my boat should weigh in at about 5000 lbs (advertised weight is 4600lbs)...

I talked with Kenny from Velocity the other day.. He was saying the open bow version of my boat he built would likely be a few MPH slower than mine with same power...

That one runs 94 MPH with about 750hp (600sc with Whipple upgrades)
He's running an Imco SCX with the SC lower 1.5 ratio with a 28 pitch Hydrmotive P5X..
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Old 01-15-2017, 06:02 PM
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Do you have full hydraulic steering ?
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Old 01-15-2017, 06:25 PM
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Originally Posted by GPM
Do you have full hydraulic steering ?
Only single ram currently...

I plan on adding another cylinder and changing the helm..

I also plan to install an Imco gimbal ring and HD helmet ...


(I broke the gimbal ring on my Corsa at 85mph.. wasn't fun.. not taking chances this time...)

Last edited by Boatally Insane; 01-15-2017 at 06:28 PM.
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