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Can it work? -- 350hp w/2.68 gear reduction

G

gatorb

Member
I am piecing together an airboat with a 350 Chevy 350hp, coupled with a 2.68 gear reduction. Do I have enough horsepower to turn the 2.68 gear? I do not have a prop yet, any suggestions? This is all going on a 16' Alumitech hull.

Does anyone know of a similar application or boat, does it work?

Thank you for your input,
Gator
 
Gator,

It depends on what type of running you are going to do you can spin the 2.68:1 but make sure you try a few different prop combinations. I'll say this and I know people are not going to like it but if you are going to run a 3 blade "S" superwide then I wouldn't spin it past about 1600-1650. I would seriously try the "K" series and as a matter of fact Sensenich is coming out with a new design that has the swept tip and it is quieter and has more thrust than the current "K" but if you decide to run a "K" you don't want 2.68 I would go with no more than 2.38.

If you want to get crazy quiet and push like the devil run a 3.12 with a four blade "S" and run like Swoosh........
 
Gator,good to see you joined 8) You`ll get alot of feed back on this one :D Sure hated to let that box go,but that`s how it goes sometimes.My opinion still stands on a 3 blade k.I`d wait for that new swept design,it will likely push harder.Or if you can find someone close,try a 2 blade super wide from one of the prop manufactures.Any way you go I think you`ll be happy.But if you get that caddy right put it on with a 3blade S from sensenich and hold on! :twisted:
 
A 2bl 76 or 78 max or sw s would be a snappy hard pushing setup! If you go with the k or falcon i suggest a 238 unless your 350 is built then go for it. I do :D
 
the whole idea of the 268 is so you can swing more prop with less hp/tq with tq being the more important# hp being how fast you can hit the wall,tq being how far you can push the wall, it also depends on size an wt of your boat anwhat you like it to do ive been in this long enough to know if ya want a boat that will doit all ,spin on a dime ,pound ground ,slow cruse deep, haul ass, haul lots of asses, be super quiet , you'll probaly have to have at least 3 boats or just find a middle ground ,jmo . isay 238 shorter med size blades or 268 with longer med size blades i recommend water walker they seem to produce more thrust with less effort by design again just my experance good luck.
 
Duece if you had a 383 bottom end built or 400 with the right cam and put your heads and accessories on top of it . I think you would be were you want to be. May not cost as much as you think if you shop around?
 
Duece, dan might be on the right track here. It sounds like your boat is doing much more for you with the 268 than the 2:1. More low end push, Cruising better and quieter, and hauling more of a load. But there is only so much you can get out of 355 HP. A 14ft DB is a pretty good size boat also, Florida Cracker has the same hull with a small block on it and his weighed in at 2400lbs. He has the 383/425 HP.
 
well I have a almost bone stock 350 with a 2.68 and a super wide q and I can swing it and so far I have not got it stuck and only spin my motor 4400 wot pitched on the #2 mark

as for when it had the 2.12 we got stuck if a frog $hit in front of the boat so the 2.68 was the best thing i ever done
now if I just put some horse power on it I would love to see it fly
 
i think the term is beat a dead horse but thunder you did raise some ?s in a post not long ago about lower hp the 268 an the superwide kinda muddied the water for some newer members and blade selection is scary considering the money
 
plumcrazy":3k5b97nt said:
i think the term is beat a dead horse but thunder you did raise some ?s in a post not long ago about lower hp the 268 an the superwide kinda muddied the water for some newer members and blade selection is scary considering the money
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I think you're referring to one of my threads.

The problem with my setup was the prop was set on one when I go it. Set up like that, I was having to rev up close to 2K just to no-wake. Surprisingly to me, I was only able to turn around 5,300 even with that small amount of pitch.

Resetting to the two mark has made my boat totally different. I now do a good no-wake (all of these are deep water numbers) at anywhere from 1200-1400 rpm. I cruise at ~3K. I run dry without a strain. It now turns 4,900 when I first get on it and climbs to a little less than 5100 if I hold it long enough.

Complaints? I'd like a little more snap and it's not as velvety smooth as my old Alumitech with belt drive and stacked Ivos.

I'll just say again, I think the S needs more pitch and less speed than other props to be effective. I'm satisfied as is, but I'd be curious to see how it would perform with a 3.12 box and even more pitch.
 
well I have a almost bone stock 350 with a 2.68 and a super wide q
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Is your prop a "S" Superwide or is it a "Q" ; huge difference.

Its really confusing the newbies that do not know the props that well. I would hate to see some one go out with out asking and get a 2.68 and try to put a "Q" on it that would be a costly mistake.
 
A 2.68 gear ratio will make up for weak motor! I would rather have a weak motor with a 2.68 ratio then a strong motor with a 2to1 ratio anytime!
 
I have a 3 blade SUPER wide the widest prop they make turning 4400 wot pitched on the #2 mark 80"
airboats_01-07_037.jpg
 
I run a 14 by 7.6 hamant with polymer
When i ran the 2 blade super wide I was spinning it at 4900 wot with a 268 and it was pitched at the # 2 mark but was turning to many rpm going down the river to do 30 mph was turning 4600 rpm

all I did was ad 1 more blade and it made all the difference in the world now with it pitch at # 2 i spin 4400 wot and my cruising speed is now to run at 30 mph I turn between 2800 and 3100 and it runs dry (NOW)

but all boats are different so what works for me my not work for you But I'm more than happy with my boat now

and my motor only makes about 300hp
I have a almost stock 350 that is 30 over with an aluminum intake and the truck it came out of stock only made 260hp
 
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