my bravo outdrive gear experiment
08-07-2006, 11:09 PM
#81
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Re: my bravo outdrive gear experiment
Originally Posted by articfriends
My understanding is other than small changes from propellor effieciency the boat should go exactly same speed with a 30 pitch prop at 6000 engine rpm's w 1.50 ratio as it would at 6000 rpm's with a 27 1/4 pitch w 1.35 ratio. How much the load would change I'm not sure.If you take my peak tq of 960 ft lbs X 1.18 (19 div by 16 for the top gear ratio) you would have 1132 ft lbs of twist on the lower pinion gear teeth no matter what ratio you had after that except load theoretically should be about 15% less but once you factor in the fact the prop will be turning 15% faster the load should be the same,but this is all just using the W.A.G method 
. If anything I would figure the prop shaft would have 15% less twist acting on it,but Ive never twisted one off so it would be a moot point. I do know this though,with these forged,beveled tooth non helical gear sets you pretty much only have one tooth contacting another at anyone time so I'm thinking thats where the problem lies. Strip brought this up a long time ago and it makes sense,aside from deflection that could be occuring,there is just 1 little tooth at any given time transmitting over 1000ft lbs of multiplied tq so it seems for it to last it would take the very best alloy and heat treating or surface conditioning,Smitty
. If anything I would figure the prop shaft would have 15% less twist acting on it,but Ive never twisted one off so it would be a moot point. I do know this though,with these forged,beveled tooth non helical gear sets you pretty much only have one tooth contacting another at anyone time so I'm thinking thats where the problem lies. Strip brought this up a long time ago and it makes sense,aside from deflection that could be occuring,there is just 1 little tooth at any given time transmitting over 1000ft lbs of multiplied tq so it seems for it to last it would take the very best alloy and heat treating or surface conditioning,SmittySmitty here is some info I got from Hustler . A 388 Hustler with 500efi 1.50 gear turns 5250-5300rpm 30 pitch bravo 4 blade doing about 85-86MPH. They told me the same boat with a 1.35 gear ratio proped [26 or 28] to turn the same RPM is slower .Hustler said the 1.50 was faster. I guess it has to do with TQ mutibles and/or like Brett at B Blades said the 30 pitch 4bl bravo was the most efficient pitch in the bravo line .
Rob
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08-08-2006, 07:24 AM
#82
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Re: my bravo outdrive gear experiment
A 1.35 gear will spin the prop faster so you will lose some hp to the water due to more friction. It will reduce the load on the gears by about 10% by allowing the use of a lower pitch prop. Or you can just pump up the hp by 10 %.
08-08-2006, 08:45 AM
#83
Re: my bravo outdrive gear experiment
Originally Posted by PatriYacht
A 1.35 gear will spin the prop faster so you will lose some hp to the water due to more friction. It will reduce the load on the gears by about 10% by allowing the use of a lower pitch prop. Or you can just pump up the hp by 10 %.
Boost
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
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The Only Time You Have To Much Ammo Is When Your Swimming Or On Fire.
08-13-2006, 09:43 AM
#84
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Re: my bravo outdrive gear experiment
Sent a set of gears out to be treated and finished with a different method,We'll see what that does. Ran boat with the 1" drive spacer yesterday,airs bow out nice again,cavitation is gone,porpoising is gone. Hard to believe 1" could make such a difference on a boat that has such a deep propcenterline to hull dimension to start with. Will see how boat handles in rough water and if top end is back soon and post,Smitty
Last edited by articfriends; 09-20-2006 at 03:09 PM.
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09-04-2006, 11:59 AM
#86
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Re: my bravo outdrive gear experiment
If you want metallurgy info check out pirates 4x4 site.
I believe the best gear treatment would be thru hardened-then induction hardened.
I'm not sure if you can do it to that kind of metal.
4340 would be superior. 300m even better. 300m is what the F1 (cars) teams are using in the gearboxes.
I believe the best gear treatment would be thru hardened-then induction hardened.
I'm not sure if you can do it to that kind of metal.
4340 would be superior. 300m even better. 300m is what the F1 (cars) teams are using in the gearboxes.
09-05-2006, 07:08 AM
#87
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Re: my bravo outdrive gear experiment
Hey Smitty,
This has been a great thread and I am cheering for ya.
I wanted to ask you where you picked up the spacer for the drive?
Dwight
This has been a great thread and I am cheering for ya.
I wanted to ask you where you picked up the spacer for the drive?
Dwight
09-05-2006, 06:46 PM
#88
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Re: my bravo outdrive gear experiment
Originally Posted by Whitey
Hey Smitty,
This has been a great thread and I am cheering for ya.
I wanted to ask you where you picked up the spacer for the drive?
Dwight
This has been a great thread and I am cheering for ya.
I wanted to ask you where you picked up the spacer for the drive?
Dwight
Last edited by articfriends; 09-20-2006 at 03:11 PM.
09-05-2006, 07:42 PM
#89
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Re: my bravo outdrive gear experiment
Originally Posted by Pantera28-650HP
Good luck Smitty!!!
If you get a chance, still interested in your build sheet.
I also had a question, I bought new 55# injectors, what do you think they are good for HP wise with the M-3?
Maybe I should go larger?
If you get a chance, still interested in your build sheet.
I also had a question, I bought new 55# injectors, what do you think they are good for HP wise with the M-3?
Maybe I should go larger?
http://www.injector.com/injectorselection.php
http://www.csgnetwork.com/fiflowcalc.html
09-05-2006, 09:15 PM
#90
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Re: my bravo outdrive gear experiment
Thanks for the info Smitty. I need a 2 inch spacer and am looking around for one. I am just not ready to buy it new....yet.
Are you staying at Brower?
We are heading there on Friday. Hope to see ya there Dwight
Are you staying at Brower?
We are heading there on Friday. Hope to see ya there Dwight
