Size Prop 350 stock DD

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Swamp Knox
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Size Prop 350 stock DD

Post by Swamp Knox »

New to airboats, currently building first! - Sumter County. I have learned much from these forums - thank you to all for your input!

Question: I have a 12 foot glass hull and am running a chevy sb stock 350 DD. Have been looking into the wooden props as they fit my budget. From reading the various forums I have narrowed it down to a 72'/32 - 34. Am I on the right track here?

Thanks
Last edited by Swamp Knox on Thu Jul 23, 2009 8:56 pm, edited 1 time in total.

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yobee
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Re: Size Prop 350 stock DD

Post by yobee »

Definitely on the right track. Look into swapping out your cam shaft (theres a few threads on here that list a couple different good DD cams) and youll be ready to rock n roll. Good luck.
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SwampMatt
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Re: Size Prop 350 stock DD

Post by SwampMatt »

72x32 if it's stock and if you build it up a bit like with a RV cam for power at low RPM then the 72x34

be sure to remember that motor will never go over 3000 rpm. That figures into your power and HP calculations. Been some talk here before about a 350 making 325 HP etc... yeah right @ 5500 rpm!! with only 3000 that's 200 HP if you are lucky. Probably less than that.

We run a stock 350 with a 72x32 and were actually thinking of going to less of a prop (72x30) so we could spin a few more RPMs and get a little more power. But we're turning the 32 @ 2800 rpm now. and it's a 3000 limit on the wood prop's warranty and safety. so we decided to stay where we are! (besides, it is already loud enough. A faster spinning prop makes more sound)

Make sure you don't have too much carb. We went wrong there too. Previous owner put a Holley 750 double pumper on that little motor!!! :shock: It don't make it run better, just burns more gas!

BTW, thanks for doing a little back-reading into the forum. So many newbies just slam in and blurt out a question that is asked every month around here! :) Welcome to the forum.

matt.

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JAMES
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Re: Size Prop 350 stock DD

Post by JAMES »

depending the work they have done to them to stock ive seen 70/34 run good as well as a 72/36
i had a stout 350 spun a 72/36 @2950 but as heavy as it was it would barley run ground maybe take off on the hill but never would run it for more then a few ft :lol: a good paddle is what id go with
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DoubleE
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Re: Size Prop 350 stock DD

Post by DoubleE »

i am running a 350 dd on a glass boat with a 70/34 and it does decent.
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mojoe
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Re: Size Prop 350 stock DD

Post by mojoe »

New to the forum, and airboating, but thought it was worth mentioning... ...I also run a 350dd, but with a 72x40 and it turns it 2800 on the trailer. The difference is mine is a stick prop(thin wood blade). The previous posts I am assuming are for wide blades. Apparently a big difference in pitch from fat to thin.
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DoubleE
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Re: Size Prop 350 stock DD

Post by DoubleE »

yeah mine is a paddle
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lanny haff
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Re: Size Prop 350 stock DD

Post by lanny haff »

On my DD350 Ihad cut down 76-38 to 66-38 I also had a small carb, low RPM cam = hi-comp pistons. Iran really good It was on a11 1/2 x 7 1/2 fiberglas hull. Lanny Haff

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CactusJack
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Re: Size Prop 350 stock DD

Post by CactusJack »

If you make a mistake, accidently go a little bigger in diameter than smaller.... you can always trim a bigger one down (diameter) you can't add to a smaller one if you really needed it to be a bit bigger :oops:

Same with pitch.... if you start with a prop with too little pitch.... too bad, your stuck with not enough pitch.... If you have a little too much pitch a manufacturer might be able to lessen the pitch a little (slightly re profile it for you), or the diameter can come down a bit.....

If you buy it too small and/or not enough pitch..... you will have to buy another prop.... end of story :roll:

Maybe see if you can buy a wood/alloy hub adjustible? I have the hub for one here, just no blades, so you should be able to get one over there?

Just my thoughts, just something to think about...... I am a noob too :oops: :D

Good luck :wink:
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BLOODSPORT
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Re: Size Prop 350 stock DD

Post by BLOODSPORT »

personally I would look for a used composit prop instead of a wood...u might be able to find a used one in good condition for about the same price...and every instance they will out perform wood any day....plus if u do more to you motor than you can adjust your prop later...just a thought

also asking for some advice...I recently got a another boat with a 500 caddy.....before I had a big block but it measures 72.5'' tip to tip on the power shift 2 blade...I dont know the degreese it is set for but does any one have a good guess as to my HP.... this is my first caddy and I have no clue

Thanks

snookwhispier
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Re: Size Prop 350 stock DD

Post by snookwhispier »

i run a 350 dd i swing 72 x 36 paddle at 2900

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barbwire6999
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Re: Size Prop 350 stock DD

Post by barbwire6999 »

well for what ever it worth, I had a 14' gilleo wide nose with a 1976 el camino sbc 350 bone stock from the junk yard and had a 76x36 spinning about 2800 and the boat would move. and my friend has a 13' lazer with a sbc 30 over 420 cam and spinning a 72x34. hope this helps a little.

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