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Two Speed Transmissions

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Old 06-08-2006, 04:26 PM
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Default Two Speed Transmissions

What are the performance gains using a twospeed transmission. I am running a v8 hammerhead diesel. [email protected] rpm 500f/lbs @1700. Will the two speed increase my topend? What drive will I have to use currently running BravoX.

Who makes the transmission
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Old 06-08-2006, 05:25 PM
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Default Re: Two Speed Transmissions

What was explained to me was that top speed is the same. What the 2-speed does is drastically reduce the plane time, like starting out in first gear of a manual car vs third, waiting until boost builds up and then the turbo lets loose. I was told that the 2 speeds often break, (which I am trying to do further reserch) and not needed if you have vent tubes. I was told from Nortech that the plane time on a 13k 4300 V is 7-8 seconds w/vent tubes. I had looked at those Hammerheads, triple version w/asd-7's, to bad the 400hp version wasn't out yet in production. Im looking at going with twin 480 Yans and Asd-8's. I'm sure more educated people will chime in. Good luck with your project. Jeff
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Old 06-08-2006, 05:26 PM
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Default Re: Two Speed Transmissions

Only way a transmission could help would be if you could prop it taller. Lets say you get a 2 speed powerglide (they are light and can be shortened,plus can be easily built for 1000 ft lbs tq and 1500 hp) or any similar 2 speed marine transmission,high gear would still be 1-1,so your boat would have to be able to pull more prop than it currently does. If thats true you could prop it taller then use low gear for maneuvering and backing up. But If your boat could pull more prop on the top end you would probably already have it on there,and with your tq peak at only 1700 you wouldn't need a lower gear to give it any "extra"bottom end. I Think I know what you really would like and that would be some type of marine transmission with overdrive but that would be a custom built very exspensive deal,you'd be far ahead to re-gear outdrive taller if your running out of prop and need less rpm's,Smitty
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Old 06-09-2006, 07:35 AM
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Default Re: Two Speed Transmissions

We run 2 & 3 spd trans with the yanmars is this a cat or v youre working with? the bravos are hoding up real well with the 440 in a cat with a 2 spd .. when you shift 2nd gear your torgue drops down.. helps the drive live .the trans we run are overdrive units..a powerglide does not have overdrive..would not benefit you as much..with a diesel you need prop shaft spd.thats where the o/d trans come in.. we have some 2 spd zf o/d units we just removed from a boat to install 3 spd into..they are set up for a bravo .. actually have a coupler for the shaft,and a rear motor mount for the two bolts on the transom assy.. cool little unit works with 12v. switch.. really neat to use..
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Old 06-10-2006, 08:11 PM
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Default Re: Two Speed Transmissions

Thanks for the advise guys. Looking to put together a setup that would squeeze as much speed out of these Diesels. I can go with either a 1.5 or a 1.36. What advise would you guys give on prop selection. 4 Blade or 5? thinking between 28 and 30 pitch on the 1.5 ratio. Not sure on the 1.36. Any Advise?


Jassman.

Good luck on the Project. The 400s are on hold right now due to emissions issues. A 350hp will be out in the Fall.
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Old 06-11-2006, 09:38 AM
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Default Re: Two Speed Transmissions

Rpms Rpms Rpms...question?? What Kind Of Boat?how Fast Are You Looking To Go? Keep In Mind Prop Shaft Speed..the Diesels Do Not Have The Rpm So The Lower Drive Ratio Would Be Advised .. But This All Depends On How Fast You Want To Go And What Kind Of Boat..cat Or V ????
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Old 06-11-2006, 11:38 AM
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Default Re: Two Speed Transmissions

I really like these diesel threads. Is there a tranny that will work with the 500/925 Yanmars, and be very reliable. I am starting my project Monday, and want to have a very reliable package. My goals to pop up on plane relatively easy, due to the type of boating in area. My concern is will a ZF live, and if so how much are they over a typical tranny that comes standard with a ASD-8. Are these trannies larger in size and take up more room, which would mean the motor moves more forward changing C.O.G., which I need to keep further aft. Any help is apprieciated. Thank You, Jeff
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Old 06-11-2006, 06:44 PM
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Default Re: Two Speed Transmissions

Guys check this out : High HP Duramax

http://www.bankspower.com/DmaxTypeR-ProjectOverView.cfm
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Old 06-12-2006, 12:32 PM
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Default Re: Two Speed Transmissions

Ultimate Cat.

The boat is a 89 scarab 33. original weight was 7500 lbs. Target Speed is about 65-70 Steady. So If I go with the 1.5 Ratio, what prop would help us get there? From My Calculations If I were to use a 30p I should be arount 71mph @ 4000 rpm using a 1.5 ratio. with about 5% slippage. What do you guys think?
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Old 06-17-2006, 07:49 PM
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Ttt
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